A masterpiece of Nuragic architecture: astronomy, geometry and symbolism
In the territory of Paulilatino in Sardinia, stands the Sacred Well of Santa Cristina. For over three thousand years this construction has continued to arouse wonder not only for the perfection of its architecture, but also for the relationships it seems to establish with the cycles of the Sun and the Moon.
It is a work designed with exceptional geometric precision and a deep knowledge of nature. The long staircase leading to the ground floor level of water, the underground chamber covered by a perfect thòlos (the cavity of the well underground) and the small oculus open to the sky form an architectural ensemble of rare harmony, considered one of the greatest achievements of Bronze Age engineering in the Mediterranean.
If the cultic function of water now appears widely recognised, the question of the possible astronomical role of the sanctuary is very recent.
Some researchers have in fact proposed that the well was also designed as an observatory capable of recording and use celestial phenomena.
This new level of understanding have finally opened perspectives on the deep level of astronomical knowledge achieved by the Nuragic populations, which was passed down from generation to generation, to acquire epochal cosmic rhythms and knowledge.
The difficulty that contemporary archaeological science faces in studying ancient monuments stems from the fragmentation with which it views the past. The human work of the ancient past was a symbol—for example, the well of Santa Cristina was not just a well or an observatory, but a well and an observatory, and a temple, and a healing place, because the ancients lacked the level of fragmentation and separation to which we have been programmed today. Today if you study physics, you can’t be expert also of literature, and if you’re an agronomist, why should you study philosophy? Nothing could be more incorrect for the past, and the more our soul opens to understanding truth, the more sensitive we become to the invisible, the more we open ourselves to the connections between different fields, the more we become like Leonardo da Vinci or Dante. Only in this way there can be true knowledge: approaching the symbol with only the rational mind will always be a failure.
So Santa Cristina Well is probably one of the most sophisticated examples of archaeoastronomy in the western Mediterranean, comparable, in conceptual complexity, to the great European megalithic monuments such as Stonehenge or Callanish, also interpreted as places of observation of solar and lunar cycles. And even more interesting if we think that contemporary researchers have dissected, measured, and studied these monuments block by block for years with care and patience, without yet having managed to fully understand their true use and function.
Alongside the astronomical dimension of the well, as you may have understood, there is something that I have been studying for a long time: water.
Water, the central element of the sanctuary, is life, purification, fertility, healing and regeneration. The descent along the staircase towards the womb of the earth, the encounter with the body of still water and the light coming from the sky build a ritual path in which sky, earth and the underground world enter into communication through an architectural language of extraordinary effectiveness.
In this article we will analyze the Sacred Well of Santa Cristina from multiple perspectives: historical, archaeological, architectural, astronomical and symbolic.
The Sanctuary of Santa Cristina: Over Three Thousand Years of Sacred Continuity
The Sacred Well of Santa Cristina represents the heart of a wide archaeological complex that testifies to over three millennia of human and religious activity.
The area lies on the basalt plateau of Abbasanta, in the Paulilatino area, in a strategic and protected position in central Sardinia.
The presence of a perennial aquifer, combined with the geological composition of the site, made this site ideal for human settlement. Here, between the 16th and 12th centuries BC, there was a Nuragic village dominated by a single-tower nuraghe, and that’s why we can find right here the great water sanctuary.
Around the well, archaeologists have identified numerous buildings. The sanctuary included the sacred enclosure (temenos), the monumental Meeting Hut, numerous circular huts, buildings likely intended for pilgrims, priests, or ritual activities, and, not far away, the nuraghe with its vast village.
The Meeting Hut
The Meeting Hut, a circular structure approximately ten meters in diameter with a continuous seat along the entire internal perimeter, suggests that community assemblies, meetings of leaders, religious ceremonies, or collective decisions were held there. In other large Nuragic sanctuaries, similar buildings have been interpreted as meeting places for communities from different parts of the island, almost a sort of federal center where religion, politics, and economics intertwined.
Alongside the ceremonial buildings, rooms reminiscent of the so-called “festival enclosure” of the sanctuary of Santa Vittoria di Serri have been identified. These structures suggest that during the main religious festivals, the sanctuary also hosted commercial activities, product exchanges, community meetings, and large ritual banquets. The pilgrimage therefore had not only a religious function, but also constituted a moment of social and economic aggregation for the entire Nuragic Sardinia.
The Nuragic Village
About two hundred meters from the well stands the Nuraghe Santa Cristina, a simple tower built in the Middle Bronze Age, around which a large village developed.
The nuraghe, approximately six meters high, still preserves its internal chamber covered with a tholos, while the surrounding remains of numerous huts from various phases of occupation emerge.
Some elongated structures visible today appear to date to later periods, likely Roman or Late Antiquity, demonstrating that the site continued to be frequented for many centuries. Even a Byzantine tomb discovered near the nuraghe’s entrance attests to the area’s long-standing settlement continuity.
This continuity suggests that Santa Cristina was not merely a temporary religious center, but a place firmly rooted in the life of local communities, whose importance survived even the end of the Nuragic civilization.
From Nuragic religion to Christianity
Between the 11th and 12th centuries, a small church dedicated to Santa Cristina di Bolsena was built next to the Nuragic sanctuary, from which the entire complex takes its name. Tradition attributes its construction to the Camaldolese monks, who also built the characteristic village of muristenes (or cumbessias), small dwellings intended to accommodate pilgrims during religious novenas, a tradition that is still alive today.
The Nuragic sanctuary and the Christian one coexist in the same space. A few steps lead from the monumental Bronze Age architecture to the sober medieval church.
The Continuity of the Sacred
When a place is perceived for centuries as particularly significant—due to the presence of a spring, a mountain, a cave, or a monumental tree—subsequent religions often tend to reinterpret its meaning rather than abandon it completely.
Spring water is one of the most obvious examples of this symbolic continuity. Water is a direct manifestation of the Earth’s vital forces: a source of life, fertility, healing, and regeneration. It is therefore not surprising that many Nuragic sanctuaries arose precisely around perennial springs, considered privileged places of encounter between the human and divine worlds. Water is the main profound symbol of the principle of life, purification, and rebirth (we all know the studies of scholars such as Chevalier, Neumann, Gimbutas, and Eliade etc).
In the beginning, there is water, with the sky and the earth; light comes later. The seed nourished under the soil by water germinates, and powerful, with nascent vigor, rises in the darkness in search of light, that is, the solar manifestation of divinity. Therefore, in the beginning, life needs only water; only later does light contribute to sustain it. So it is in the mother’s womb.
Today we know well that the further we are from the primary source of water, the more the water loses its properties of purity, mineral richness, electromagnetic field, ionization (see also the article on the Hunza valley where they had no wells and the water is taken directly from the glacier).
So when we dug to reach the water underground, at a certain point we can found the level of stillness, of stability: this is the level of the divine, in which the water flowed from the earth in equilibrium: the level of pristine water, today we would call it.
To find the aspect of the sacred that is expressed in balance and gentleness, the person has to descend into the bowels of the earth, enter the darkness and climb the descending ladder.
With the rise of Christianity, this symbolic heritage was not completely erased. On the contrary, it was largely reinterpreted, like in Jewish religion, Hinduism and then Islam, through ablution with water, that is baptism, and in Christianity the politheitic pantheon of the pagan gods created the cult of saints, and the veneration of waters considered miraculous.
See also my article about sacred wells in India.
Water wells are often connected with goddness (Astarte, Diana, Aphrodite, nymphs…) and in Chrstianity they become Holy Mary, Santa Lucia, Santa Cristina etc.
Saint Lucia is the protector of sight, and water sources often report miracles related to eyes problems.
Building churches over ancient places of worship
The construction of a Christian church at the sanctuary of Santa Cristina is part of a well-documented phenomenon in European history.
Between the 6th and 7th centuries, for example, Pope Gregory the Great, in his famous letters to the missionary Mellitus during the evangelization of England, recommended, whenever possible, not destroying pagan temples but purifying them and transforming them into places of Christian worship. The goal was to encourage a gradual conversion of the populations, preserving the familiarity of the places while giving them a new religious meaning. People were programmed, in the past as today, for the prupose of the rulers of the society. This pastoral directive is one of the most important documents for understanding the missionary strategy of the early medieval Church.
The geometric structure
The azimuthal orientation of Santa Cristina is 153°08‘.
Azimuth is the angle that indicates a direction relative to true North. Astronomers and surveyors measure azimuth clockwise:
0° = North
90° = East
180° = South
270° = West
Therefore an azimuth of 153°08′ means that the axis of the monument points towards a direction between East and South, i.e. towards the South-East.
The stair is not a perfectly straight corridor.
Descending the width increases, the steps progressively widen and a sort of fan shape is created.
So we can measure the azimuths of the two extreme sides of the staircase.
They range from: 132° to 174°
Therefore, the staircase sees a sector of the horizon approximately:
174° − 132° = 42°
Therefore the well is illumintated in the morning from the sun rays entering from the stairs.
The descending stair is inclined, and the ramp forms a zenith angle of approximately 52°.
The zenith angle is measured from the vertical.
So 90° − 52° = 38°
Therefore the scale is inclined as if it were looking at a star placed at 38° above the horizon.
On the days close to the equinoxes, when the Sun reaches a position of approximately 152° azimuth and 38° above the horizon during the morning, its rays can travel along the stairway until they reach the underground chamber and the surface of the water.
The azimuthal orientation of the sacred wells is not always the same, for example that of Funtana Coberta is approximately 240°43′, therefore the first is illuminated inside in the afternoon.
However, the two wells have one thing in common: the 12th anomalous ring is higher than the others.
The Underground Chamber
At the end of the 22 steps – stairs lies a perfectly circular chamber, excavated to intercept the natural water table.
The chamber measures approximately 2.5 meters in internal diameter and is covered by an extraordinary tholos, approximately seven meters high, culminating in a small oculus approximately 35 centimeters in diameter. These seemingly simple proportions are actually the result of extremely meticulous planning, in which each measurement appears to maintain well-defined geometric relationships with the others.
The chamber’s perfect circularity contributes to a sense of balance, protection and harmony. Water occupies the center of the construction, becoming the visual and symbolic fulcrum of the entire monument.
The Tholos: A Dome Built Without Mortar
The most extraordinary architectural element of the Pozzo di Santa Cristina is undoubtedly the tholos (from the Greek θόλος, thólos, “dome”), a unique false dome roof achieved through the progressive overhang technique.
Unlike a true dome, in which the weight is distributed through radially arranged arches and ashlars, the tholos is built by stacking concentric rings of stone blocks. Each row protrudes slightly inward from the one below, progressively narrowing the diameter of the structure until only a small opening at the top, called an oculus, is left. The entire building is supported solely by the balance of weight and the extreme precision with which each block was worked and positioned, without the use of mortar or other binders, as in the most of ancient monumets of the past.
In the Pozzo di Santa Cristina, this technique reaches one of its highest levels of perfection. The underground chamber, approximately 2.5 meters in diameter and approximately 7 meters high, is covered by a tholos composed of 22 concentric rows of perfectly squared basalt blocks. Each ashlar is slightly set back from the one below, creating an extremely regular geometric progression that leads the eye to the small circular oculus opening to the sky.
The quality of the workmanship is astonishing. The basalt blocks were carefully polished and fitted with such precision that the joints are minimal. After over three thousand years, the structure still retains exceptional stability, demonstrating the extraordinary technical expertise achieved by Nuragic architects.
Each ashlar has a slightly inclined external face and protrudes about one to two centimeters from the block above, creating a refined serrated profile that guides the eye upward and with the moonlight shows an effect like a stair of light. This feature is also present in other sacred Nuragic wells, but in Santa Cristina it reaches an unparalleled level of perfection.
From a static perspective, this solution distributes the weight of the covering along the entire wall, avoiding load concentrations and increasing the stability of the entire structure.
From an aesthetic perspective, however, it creates an effect of progressive lightness: the masonry seems to narrow almost naturally until it opens up into the small circle of the oculus.
From an astronomic perpective, it creates minimal grooves on which the moonlight is refracted, creating the effect of sequential levels of light. At the center of the tholos is a layer of ashlars higher than the others, and we will see how this too naturally serves a specific purpose.
The tholos technique was not unknown in the Bronze Age Mediterranean. Famous examples include the large Mycenaean tombs, such as the so-called Treasury of Atreus in Mycenae, built between the 14th and 13th centuries BC, and several monumental tombs in Anatolia. There are many similarities in the construction techniques of the Nuragic monuments in Sardinia and the Mycenaean ones, so it is natural to think that these incredible seafaring peoples, great experts in the Mediterranean, traveled easily by ship, helped each other and traded with each other, as was the case with the Greek architect who created the statue of the young man at Motya in Sicily for a Phoenician city.
In Sardinia, too, the tholos roof appears in the interior chambers of nuraghes, but in the Pozzo di Santa Cristina it reaches a level of refinement rarely matched. The perfect regularity of the rows, the precision of the joints, and the elegance of the proportions make this construction one of the absolute masterpieces of European megalithic architecture.
The small oculus at the top of the dome is the only opening to the sky. Sunlight penetrates through it during the equinoxes and, according to the studies of archaeoastronomer Arnold Lebeuf, also moonlight during particular configurations of the major lunistic cycle. From this perspective, the dome is an integral part of a sophisticated astronomical observation device, capable of transforming the sky into a living element of the architecture itself.
It is precisely this dual nature, technical and symbolic, that makes the tholos of the Pozzo di Santa Cristina a unique work. It protects the spring, supports the land above, frames the sky and, at the same time, creates an ideal connection between the underground world of water and the celestial vault, merging architecture, engineering and cosmology in a single structure.
The choice of basalt was not accidental. This volcanic rock, extremely hard and resistant to atmospheric agents, allowed for perfectly worked surfaces and guaranteed remarkable durability over time.
Light as an architectural material
The well is one of the very rare Bronze Age buildings in which natural light becomes an integral part of the architectural design.
The temple is always alive, because is part of nature.
The oriented entrance with the stairs, the long staircase, the underground chamber, and the oculus of the tholos are not independent elements, but parts of a single spatial composition. For most of the day, the interior remains immersed in almost total darkness. At certain times of the year, however, a thin beam of light passes through the monument, completely altering its perception.
This relationship between stone, darkness, and light is one of the most important aspects of the well’s architecture and anticipates the theme we will explore in subsequent chapters: the building’s possible astronomical use.
Nearly a hundred sacred Nuragic wells are known in Sardinia today, distributed across much of the island. Many of them share common architectural features, such as the underground staircase, the circular chamber, and the tholos roof.
The Well of Santa Cristina occupies a very unique location because of the quality of the ashlar workmanship, the perfect symmetry of the construction, the accuracy of its proportions, and its extraordinary state of preservation make this building an absolute masterpiece of Nuragic religious architecture. It is therefore not surprising that numerous scholars have called it one of the most perfect stone structures built in Bronze Age Europe.
The ritual function of water in the Nuragic religion
The veneration of springs and groundwater is a widespread phenomenon in all the ancient cultures of the Mediterranean. The water that flows from the depths of the earth possessed a particular character: it was a reality coming from a hidden world.
In ancient religious traditions the spring often represented:
the meeting point between heaven, earth and the underworld;
the place where divinity could manifest itself;
a source of healing and purification;
a symbol of cyclical rebirth.
In the case of the Nuragic sacred wells, this dimension seems to have been particularly developed. The water was reached through a ritual descent, almost a journey to the heart of the earth.
To reach the water, to reach life, you have to descend, not ascend. A very interesting perspective, one that has been somewhat forgotten today after the spread of Jacob’s ladder and ascensions to heaven. Yet where there is a ladder above, there is also a ladder below, and the well of Santa Cristina reminds us of this very well, with the double ladder at the entrance, one above your head and one below your feet.
To reach the water, one must descend a staircase composed of numerous regular steps, enclosed by perfectly crafted walls that lead progressively downward.
This configuration creates a unique spatial experience:
the person leaves the illuminated surface of the everyday world, gradually enters the darkness of the subsoil and reaches the point of water, located at the center of the structure. Then there is the return to the external light.
The sequence recalls a universal symbolism: the descent into the depths of the earth as a symbolic discovery of a new self (or the mistery of life and nature) and the subsequent ascent as renewal.
Many ancient cults used underground passages or enclosed spaces to represent a transformative passage. In Greek mysteries, fertility cults, and Mediterranean traditions of the Great Mother, the return from the depths represented the renewal of life.
In the Nuragic well, this idea could be expressed through the relationship between:
earthly depths → womb of the divinity;
hidden water → generative principle;
light of the sky → cosmic order.
The very shape of the monument possesses strong symbolic value.
The underground chamber tholos (the a circular structure covered by a false dome created by progressively protruding stone blocks) evokes a protected cavity, a closed and generative environment: a womb.
The association between cavities, water, and fertility is ancient.
The earth is often depicted as a living organism:
- the surface is the world inhabited by humans;
- the depths are the place of gestation;
- the underground water is the hidden vital principle.
Entering the well therefore symbolically means entering the Earth’s matrix, where water holds the power of regeneration.
The worship of water is a space connected to the great natural cycles: agricultural fertility, the birth of animals, the continuity of the community, and the renewal of the seasons.
Archaeological excavations near Nuragic sacred wells have yielded numerous votive objects, especially small bronzes, metal objects, and religious artifacts.
Among the most frequent offerings are:
- human figures representing warriors, leaders, worshippers;
- symbolic animals;
- votive vessels;
- miniaturized weapons;
- everyday objects transformed into ritual gifts.
These objects suggest that the well was a place of ritual communication: the offering was entrusted to the water or placed in the sacred space to establish a relationship with divine power.
The act of offering likely had several meanings:
- a request for protection;
- thanksgiving;
- invocation of fertility;
- healing;
- celebration of important events in the life of the community.
We have no written texts from the Nuragic civilization describing the rituals performed in the sacred wells, so any interpretation must be based on archaeological studies and comparisons with other ancient cultures and religions.
However, the architectural complexity of Santa Cristina indicates highly specialized knowledge.
The construction required advanced geometric skills, hydraulic knowledge, organization of collective work, and an understanding of celestial and seasonal phenomena.
It is possible that a class of religious specialists—cult custodians—managed the ceremonies related to the well, regulating specific times of the year according to agricultural and astronomical calendars.
In this sense, the sanctuary could simultaneously be:
a place of worship;
a community center;
a space for observing natural weather;
a spiritual reference point for the area.
The Well of Santa Cristina is designed so that sunlight can penetrate the structure according to precise astronomical conditions. This relationship between celestial light and underground water creates an extremely powerful cosmological image: the Sun in the sky meets the water hidden within the Earth.
At specific times of the year, the light beam descends into the circular chamber, transforming the sacred space into a meeting point between two dimensions:
- the upper world, governed by the stars;
- the lower world, governated by water.
This relationship will be fundamental to understanding the role of the equinoxes, solar cycles, and lunar phenomena, which we will analyze in the following chapters.
The Well of Santa Cristina could therefore be read as an extraordinary stone representation of the Nuragic vision of the universe: a structure where human geometry becomes a means of dialogue with the rhythms of the cosmos.
The alignments of the well: archeoastronomy
To understand the luminous phenomenon, we must first remind the structure.
The Sacred Well of Santa Cristina consists of three main elements:
1. The upper vestibule
This is the entrance area, located outside the well.
Characteristics:
- Trapezoidal shape;
- South-facing entrance;
- A space likely intended for ritual preparation;
- A transition point between the profane and sacred spaces.
2. The monumental staircase
The staircase leads down to the water chamber.
Generally reported measurements:
22 steps;
Width approximately 1 meter;
Depth of the steps very evenly;
Walls constructed of perfectly shaped blocks.
The descent creates a particular effect: whoever enters progressively loses contact with the external environment and approaches a point completely dominated by geometry.
3. The Tholos Chamber
At the end of the stairs is the circular chamber.
Approximate dimensions:
Internal diameter: approximately 3.5 meters;
Height: approximately 7 meters;
Circular plan;
False dome roof.
The false dome is constructed with rows of stones that progressively project inward toward the upper end. The 12th level of stone is bigger then the others.
This technique is not only functional: it creates a perfectly centered, almost astronomical geometry like a telescope.
THE EQUINOXES
During the equinoxes, the sun exhibits a particular characteristic:
- it rises exactly in the east;
- it travels a symmetrical arc across the sky;
- it sets exactly in the west.
This moment represents a cosmic balance: all the ancient cultures considered the equinoxes moments of important energy, it was the end of winter and the rebirth of spring (spring equinox – aries); or the the end of summer and the beginning of the dark season (autumn equinox – libra); the balance between light and darkness.
For an agricultural society like the Nuragic one, these calendar points were of enormous importance. The astronomical hypothesis made by researchers holds that in the days surrounding the equinoxes, the sun can illuminate the interior of the chamber following a particular trajectory through the ramp.
This is not completely true, since for the latitude of the Pozzo di Santa Cristina (about 40.1° N), at the equinoxes when the Sun reaches an azimuth of about 152°, its altitude is about 46°, not 38° (the zenith angle of the ramp).
This difference is too great to be ignored.
Anyway in general around the days of the eqinoxes (and not only in these days) is true that the sun rays can penetre the well, with an optic effect of doublig the shadows of the well parts and also creating the appearance of an inverted shadow of the observer: we can see ourselves reflected in the water and at the same time also our own upside down shadow generated by the sunlight entering both from the oculus and from the stairs.
The inverted shadow: the opening of the thòlos works like a small optical hole
The well chamber is a dark environment with only one opening towards the top.
When a dark room has a small opening through which light enters, it can behave like a darkroom of a camera.
It is the same principle that allows ancient darkrooms to project images.
Imagine a completely dark room with a small hole in the wall:
the light coming from the upper part of the landscape enters through the hole;
passes through space;
it hits the opposite wall;
the image appears upside down.
Because the light rays travel in a straight line and cross each other passing through the hole.
This is exactly what happens in our eye: the image on the retina is upside down and then our brain flips it over.
Studies of Archeoastronomy: Sandro Angei
Sandro Angei interprets the well as a monument capable of recording different hierophanies (manifestations of light and divine) throughout the year.
In the days roughly between April 16th and 25th, peaking on April 20th-21st, a very peculiar phenomenon occurs.
When the Sun reaches a certain height in the sky, its rays:
penetrate the stairwell;
reach the surface of the water;
are reflected upward by the water;
the light reflection strikes the twelfth ring of the false dome (tholos), a stone that the author considers architecturally “special.”
According to this interpretation, it is not the Sun’s direct ray that strikes the twelfth ring, but the ray reflected by the water, which would act like a mirror.
Angei observes that precisely on April 20th and 21st, the reflection reaches that point completely; from April 22nd onward, it continues to enter the well, but no longer reaches the twelfth ring. For this reason, he considers April 20th-21st a sort of “signal date” for rituals, agriculture or something we lost.
On June 21st, the day of the summer solstice, the Sun reaches its maximum annual height.
Something different happens in the well compared to April.
According to the reported observations:
the stairwell is illuminated;
at the same time, a beam of light enters from the oculus of the thòlos;
the light point moves until it illuminates the edge of the twelfth ring of the dome.
Angei believes that, around 1000 BC, due to the different inclination of the Earth’s axis compared to today (precession and variations in obliquity), the light beam illuminated the entire thickness of the twelfth ring with even greater precision. On June 21, 1000 BC, in the well of Santa Cristina, the sun illuminated the entire thickness of the 12th ring at the center of the ashlar marked by the underlying narrow ashlar.
At the equinoxes, the sun penetrates the basin but without any significant impact on the ashlar. In fact, it illuminates a portion of the wall with no particular significance, or at least so it seems.
April 21st
According to Angei’s hypothesis:
the reflection of the light on the water hits a precise point of the twelfth ring of the dome.
At the equinoxes (March and September)
No significant effect on the ashlars, apart from the doublig effect of the shadow (that doesn’t happen only in this period anyway).
June 21st
Again according to Angei: the Sun at the solstice produces a different hierophany, still linked to the twelfth ring, which would represent the culmination of a ritual cycle that began in April.
These are the best known and documented phenomena.
The luminous phenomena of the Sacred Well of Santa Cristina are not limited to the day of the equinox alone. Since the apparent position of the Sun varies gradually over the course of the year, the path of the rays within the structure also changes continuously. In the days before and after the equinoxes the light beam continues to penetrate the stairwell and reach the underground chamber, producing very similar effects. The equinoxes therefore represent the astronomical reference of the phenomenon, not necessarily the only moment in which it is observable.
The Archeologist Lebeuf proposed that:
the thòlos functioned as a sort of astronomical chamber and the well was designed to observe the lunistice; this would even allow us to follow the 18.6-year cycle of the Moon and, indirectly, to predict eclipses.
Let’s see first of all what a major lunistice is.
The lunar cycle and the phenomenon of the major lunistice
Over the course of the year the Sun slowly changes the point at which it rises and sets, reaching the two extremes at the solstices and returning to an intermediate position at the equinoxes.
If the apparent movement of the Sun is relatively simple and regular, that of the Moon is much more complex. It is precisely this complexity that has fascinated astronomers since ancient times and which constitutes the starting point of the hypothesis advanced by Arnold Lebeuf on the Sacred Well of Santa Cristina.
Unlike the Sun, which always follows the same cycle between the two solstices throughout the year, the Moon continually changes its position in the sky. Every night it rises and sets at a slightly different point on the horizon, reaches different heights and travels through celestial arcs that change from month to month.
These variations depend on the fact that the Moon does not orbit the Earth on the same plane along which the Earth rotates around the Sun. Its orbit is in fact inclined by about 5.1° with respect to the ecliptic (the plane of the Earth’s orbit).
This inclination produces an important effect: the Moon never exactly follows the apparent path of the Sun, but continually oscillates slightly further north or further south.
The Moon’s orbit intersects the ecliptic plane at two points called lunar nodes.
One is called the ascending node, because the Moon crosses the ecliptic passing from south to north; the other is the descending node, where the passage occurs in the opposite direction.
These nodes do not remain fixed in space: they rotate slowly along the ecliptic, completing an entire revolution in approximately 18.6 years.
It is precisely this slow movement that gives rise to the phenomenon of the lunistice.
LUNISTICE
The term lunistice (in English lunar standstill) indicates the moment in which the Moon reaches the maximum possible width of its apparent path in the sky.
During this period, which repeats approximately every 18.6 years, the Moon:
- rises much further north than normal or much further south, depending on the phase of the cycle;
- reaches heights in the sky higher or lower than those observable in intermediate years.
In other words, its apparent arc becomes as extended as possible.
To an attentive observer, the change is evident.
The Moon behaves in a much more complex way than the sun. Every month it continuously changes position in the sky: every night it rises in a slightly different point on the horizon and travels in different arcs.
But, in addition to this monthly cycle, there is the lunistice, a much longer cycle.
The Moon’s orbit is inclined by about 5° compared to the plane of the Earth’s orbit (the ecliptic).
Furthermore, the entire lunar orbit rotates slowly in space: the points where it intersects the ecliptic, called lunar nodes, complete one rotation in about 18.6 years.
This slow movement means that, over the course of 18,6 years, the Moon progressively reaches increasingly extreme positions in the sky, up to a maximum, and then returns to more central positions.
When the Moon reaches these extreme positions it is called a major lunar standstill.
MAJOR LUNISTICE
During a major lunistice the Moon can rise much further north or much further south than normal, it can set at points on the horizon that it does not reach in the intervening years, and it can reach a maximum height in the sky higher than usual.
In practice, the Moon’s path becomes as wide as possible.
The effect is particularly evident during the full moons close to the solstices: in those years the Moon travels through exceptionally high or very low arcs in the sky, easily recognizable by expert observers.
Because the phenomenon only repeats every 18.6 years, it requires observations passed down through generations.
During a major lunistice the Moon can appear in points on the horizon that it had not reached for almost twenty years.
There are two opposite situations.
1 – On the major lunistice the Moon reaches its maximum possible excursion.
Its declination can reach approximately ±28.6°, that is, approximately five degrees beyond that of the Sun’s maximum at the solstices (±23.4°).
This means that Moonrise occurs extremely north-east or south-east;
the sunset extremely north-west or south-west;
the height reached in the sky is exceptionally high or particularly low.
This is the phenomenon that interested Arnold Lebeuf.
2 – The minor lunistice occurs approximately 9.3 years after the major moonistice.
In this case the Moon travels in much smaller arcs.
The maximum declination is reduced to approximately ±18.3°, and its movement in the sky appears much more limited.
Arnold Lebeuf’s astronomical hypothesis and the major lunistice
Among the most recent interpretations of the Sacred Well of Santa Cristina is that proposed by the French archaeoastronomer Arnold Lebeuf, according to whom the monument was not only conceived as a sanctuary of water, but also as an observatory dedicated to the cycles of the Moon, the major lunistice.
Unlike the phases of the moon, which repeat every month, the major lunistice is a rare event.
An observer can only witness it two or three times in his lifetime.
Precisely for this reason many archaeoastronomers believe that any monuments built to record this phenomenon presuppose a long tradition of astronomical observations handed down between generations.
The cycle is now perfectly known to modern astronomers, but it was observable even without optical instruments: it was enough to record for many years the point at which the Moon rose and set on the horizon.
The theory of Leboeuf is based on the major lunistice.
According to Arnold Lebeuf, the Nuragic architects designed the Sacred Well of Santa Cristina so that the light of the Moon could penetrate through the oculus of the thòlos during the major lunistice.
In particular, he hypothesized that the perfectly symmetrical geometry of the underground chamber was not just an architectural choice; the top opening functioned as a sort of “astronomical window” and during some full moon nights close to the major moon, the light of the Moon could reach the surface of the water at the bottom of the well.
If this interpretation were correct, the sanctuary would have allowed us to recognize the culmination of the 18.6-year lunar cycle.
Lebeuf believed that knowing this cycle could also have a practical function.
Since eclipses can only occur when the Sun, Earth, and Moon are near the nodes of the lunar orbit, tracking the slow movement of the nodes would have allowed us to predict the periods when eclipses were most likely.
According to this hypothesis, the well would have represented not only a place of worship, but also a precise instrument for observing the great cycles of the sky.
Giulia Maria – Voice of Plenty