Knowth: Archaeological & Astronomical Legacy

Knowth: Archaeological & Astronomical Legacy

Did Knowth's builders possess a comprehensive knowledge of the movements of the sun and moon? It has been suggested that some carvings upon its kerb stones can be interpreted as calendrical and astronomical symbolism. The following is a summary of the archaeological and astronomical significance of Knowth (Cnogba), one of the three great passage-mounds of the Bend of the Boyne, and the largest of the three.


Newgrange has long been heralded as the greatest ancient Irish site. Its beautiful Neolithic art, impressive white quartz facade and great standing stones make it a visually remarkable testament to its ancient builders. In terms of archaeology, art, beauty and size, Newgrange is equalled by just one other monument – its near neighbour, Knowth.


Aurora at Newgrange
Aurora borealis (northern lights) at Newgrange.


A great deal has been made about the many periods of activity at Knowth over the course of millenia. Archaeology has discussed Knowth as an ancient site which, instead of decaying when its original constructors passed on, became a focal point for many different peoples, some from radically different traditions, and many from foreign countries.

Much has also been made about the great age of this site, which archaeologists tell us is 1,000 years older than Stonehenge and 500 years older than the Giza Pyramids.

During the huge span of time which has passed since the earliest dated phase of activity at Knowth, which has been placed by archaeologists at 4,000BC, the site has had varied uses, which include habitation, burial, and ceremony. What the archaeologists have been less enthusiastic about discussing, however, is the fact that the people who constructed Knowth in the fourth millennium BC, and carefully incised and picked delicate and intricate markings on the huge stones, were competent astronomers, with a level of astronomical understanding that was far better than rudimentary.

Regrettably, astronomy is not part of the modern archaeological curriculum at Irish universities. Academic archaeology doesn't tend to discuss the possible calendrical and cosmological functions of Irish passage-tombs very much, mainly because there is a reluctance to deal with the apparently complex observational lunar astronomy that might have taken place there deep in prehistory. The Neolithic complex of Knowth features a plethora of imagery and symbolism that appears astronomical in nature.

However, archaeological work at Knowth has revealed much about a mysterious culture – the people of the Neolithic – and the exploration of these many revelations, by academic and amateur researchers alike, will continue for many years to come. An interesting aspect of the exploration of Knowth's history is the fact that it has a much more varied and complicated past than its famous neighbour, Newgrange, which has become renowned right across the world, especially in light of its unique astronomical alignment with the winter solstice sunrise.

It seems that Newgrange fell into a state of disrepair, and was perhaps abandoned at some stage in the distant past, consigned to the ravages of nature and the elements, which had surprisingly little effect on the site over the following thousands of years.


A place of settlement

At Knowth, in contrast to what happened at Newgrange, the site became an important place of settlement and indeed a significant place in terms of political and military power.

Approximately one thousand years before the construction of the Knowth mound took place, there was a small settlement which has been identified from the remains of a rectangular house. It has been suggested this house was made of wood and wattle, and it dates to about 4,000BC.

Stormy Sky at Knowth
A summer shower cloud approaches the Knowth megalithic complex.


At this time, the agglomeration of cairns, mounds and stones which can be seen in the Brú na Bóinne area today did not exist. It was only in the few centuries preceeding the turn of the third millennium BC when the mound-building and stone-carving activity began.

Archaeology has termed many of these Boyne sites "passage-tombs", and there is much evidence to suggest human remains, burned and unburned, were placed in the chambers of these sites. But debate continues as to whether these burials were all carried out in the Neolithic, or at a later time, and whether sites on this scale have other purposes. The larger mounds of Knowth, Newgrange and Dowth are covered with art, or carved symbols, which have been interpreted as being astronomical in nature. This, coupled with the winter solstice solar illumination events at Newgrange and Dowth, raises some interesting questions about how these sites have been interpreted.

Paleopathologists working during excavations at Knowth suggested that the remains of up to 200 individuals were found in the eastern chamber, so certainly the evidence for burial remains very strong. However, Knowth and its sister monuments were probably designed to be much more than tombs. (See Newgrange: Monument to Immortality for further discussion of this theme).

Although the astronomical importance of Knowth almost definitely dates to the New Stone Age, it seems the later phases of activity at Knowth concentrated much less on this aspect, and indeed people who lived at Knowth in later times, such as the Norman period, may not have known much about the original intentions and purpose of the site.

The Knowth complex consists of a total of 18 sites, which have all been classified as "passage graves", but this site is just part of a much bigger grouping of sites in this part of the Boyne Valley which has been termed "The Boyne Cemetery". This group covers 10 square kilometres, with a total of 40 passage graves, and a mixture of sites, such as embanked enclosures, standing stones and other "ceremonial sites" like the great cursus of Newgrange. The area is called Brú/Brugh na Boinne, and it has been listed as a protected world heritage site by UNESCO. 

Of all the 40 mounds here, three are particularly big – Newgrange, Dowth and Knowth, the latter being the largest. Interestingly, they are all contained by the River Boyne, which makes a spectacular loop around Brú Na Boinne on its way to the sea at Drogheda. We know that the river was important in ancient times, not only because this concentration of sites was assembled along its shores, and the river was used to transport some of the materials used in their construction, but also because of the mythology which exists about the Boyne.

The ancient settlers who came here about 6,000 years ago, most probably by river, cleared the trees from Brú na Bóinne, and began growing crops like wheat and barley in the fertile soil of this area. We are told they were among the first farmers in Ireland, and that they kept cattle, pigs, sheep and goats.

We are also told that, contrary to the contemporary belief that the people of the Stone Age were primitive and savage, they were an organised society of intelligent people, who had much experience and knowledge in terms of technology and engineering (notwithstanding the relatively primitive materials and tools they used), and who were highly adept astronomers with a developed system of spiritual and religious beliefs. They were also likely to have been competent mariners, as the rivers and the sea provided the only effective means of transport in the Neolithic, and indeed were used to ferry some of the construction materials for the main monuments to the Bend of the Boyne.

Some aspects of their culture have striking similarities to Christianity, and there is some evidence to suggest that Christian settlers at Knowth may have understood the relevance of these similarities. 

Lunar function

For instance, the eastern passage of Knowth with its long passage and three recesses is cruciform in shape, suggestive of a belief system which incorporates a triple divinity, something that is reflected at Newgrange, where there is not just a cruciform passage, but also a triple spiral on the entrance stone and on another stone in the end recess of the chamber. At Newgrange, there are two triunes in myth – Dagda, Bóinn and Oengus Óg, and Lugh, Dechtine and Sétanta.

Knowth's eastern passage points to an azimuth of 85 degrees, a small distance off due east, and the reason behind this is explained by Charlie Scribner's theory about the astronomical function of Knowth.


Knowth Samhain Sunset
Sunset and red sky at Knowth around Samhain.

This proposed lunar function is supported by the theories of planetary cartographer Philip Stooke, of the University of Western Ontario, who says an engraving on a stone in the end recess of Knowth's eastern passage may be the earliest known map of the moon. Suggestions that moonlight entering the eastern passage could have illuminated this "moon map" cannot be tested, however, because this passage is blocked by a huge concrete slab, erected during conservation and restoration work at the site to protect Early Christian structures near the entrance to the passageway. Curiously, the concrete wall has also facilitated the introduction of a huge metal footbridge which allows tourists access into the mound.

Researchers like Martin Brennan and N.L. Thomas have suggested lunar and calendrical functions with regard to many of the kerb stones at Knowth. Further research at Knowth suggests a complicated lunar and calendrical system was in place here over 5,000 years ago.

The stone labelled the "Calendar Stone" by Martin Brennan was aptly named, I believe, but it goes even further than Brennan suggests in calendrical terms, and can be used to calculate the exact length of the year. Although our views of the complexity of its nature differ, we are both in agreement about what the stone actually represents – astronomy – something often overlooked by conventional archaeology, which has a tendency to introduce arbitrary and functional theories about the purpose and nature of these great monuments.

Research has shown that another stone, on which Brennan identified the 27-day siderial lunar month, also contains symbolism which can be interpreted as representing the 29-day lunar month, known as the synodic period. Both of these lunation periods are important in understanding the moon's movements, and specifically the Metonic Cycle, which we already know was marked in the Boyne Valley as a number of monuments are aligned on what are termed "standstills" of the moon.The work of Alexander Thom is viewed by many researchers as evidence of lunar studies in the Neolithic. By 1969, Thom had presented substantial evidence that some of the Stone Age alignments which singled out extremes of the sun and moon were very accurate. In the Boyne Valley, lunar interest was great, and at Knowth, as mentioned earlier, the lunar symbolism is explicit. Gillies MacBain has identified that the total number of kerb stones at Knowth (127) is half the number of siderial lunar months (254) in one 19-year Metonic Cycle of the moon.

The Christian settlers also built a structure at the entrance to the east passage, one which was incorporated into the Neolithic passage in such a way as to alter its direction. Were the Christians trying to hide something?


Knowth Kerb Stone 83
Knowth kerb stone 83 at Knowth/Cnogba.


Bronze Age lull

After the Neolithic, a major change occurred in Ireland, some time between 3,000 and 2,500BC. There emerged a much more different society, one which had developed metallurgic technology, namely bronze. Hence this period is called the Bronze Age. It was at this time that metal daggers, knives, axes, spearheads and swords made their appearance in Irish history.

But curiously, despite a huge wealth of Bronze Age sites in the Boyne Valley and wider area, there is very little evidence for any activity at Knowth during that period. Only one piece of evidence, a Beaker burial, gives any indication of activity at Knowth during the Bronze Age. Archaeologists are at pains to explain why there should be such a gap in the chronology of activity here. One suggestion, that a plague may have killed people off, seems untenable because of Bronze Age activity in other parts of the Brú na Bóinne area.

The great circle of standing stones which surround the nearby Newgrange temple are said to have been erected during the Bronze Age, so there was certainly very significant activity in the Brú area at this time. Some have suggested that the Bronze Age people held Knowth in great reverence, and perhaps fear, so they left it alone. But again, the activity at Newgrange challenges this theory. In my opinion, this aspect of the exploration of Knowth needs further investigation.

The Beaker burial belongs to a period in the early Bronze Age when the Beaker People used a particular style of pottery for domestic purposes. Beaker pottery used in the context of a burial, termed a Beaker burial, is commonplace on the continent, but this was the first such burial found in Ireland. Again, this raises more questions than it answers, and as an example of a unique cultural phase at Knowth, it is not alone. Excavations at Knowth in the early 1990s were to reveal another unique phase of activity, called Grooved Ware.

Great excitement was aroused by the discovery of the Grooved Ware phase, which was widely reported in the media at the time. Although Grooved Ware gets its name from a particular type of pottery vessel which has a flat bottom and straight sides, it is also marked at Knowth by the presence of a circular structure near the eastern passage entrance which was discovered through the presence of 33 post holes.

Situated about 12 metres in front of the eastern entrance, this so-called "wood henge" it is aligned in the same direction – towards the east. Its precise purpose is the subject of discussion and speculation, and the whole structure has been recreated using wooden posts so that tourists can see what it might have looked like.

The Celts

After the Neolithic, the next important phase of activity at Knowth was during the Iron Age, in the late centuries BC and the early centuries AD. This was the age of the Celts, who arrived in Ireland from the Iberian peninsula. This wave of immigrants is recorded in ancient mythology, and the people we can most identify with this inundation were called the Milesians, or the sons of Mil, who were said to have landed at the Boyne Estuary after a sea battle against the Tuatha De Danann. They came to Ireland from Spain.

The Celts did not show the same level of respect and reverence for the ancient stone sites as the Bronze Age people had done at Newgrange. When they came to Knowth, the Celts dug two huge concentric trenches into the mound, with some sort of enclosure at the top of the cairn. This is just one example of how the ancient benevolent culture of the Neolithic was replaced with a more aggressive and malign community. Another is the interesting find of a double burial at Knowth dating from this time, in which the deceased, two young men, had been decapitated.

One tragedy arising out of the Celtic occupation of Knowth is the fact that one of the trenches, dug inside the great kerb of stones, severely damaged the entrances to the two passages, and removed a number of orthostats, shortening both passages by an estimated four metres.

An accidental act of preservation during the Iron Age helped to negate the damage to the passages. In constructing their great circular ditches around the mound, the Celts buried the great kerb of 127 stones. They remained buried until excavations began in the 1960s, and their remarkable state of preservation is partly due to the Iron Age activity. Only three of the original kerb stones are missing.

A number of Iron Age burials, about three dozen, were found at Knowth. These burials were placed in pits dug into the ground, and were often accompanied by grave goods.

After the Celts, there was a lull in the level of activity until the next major phase of settlement, which occurred in Christian times, between the eighth and twelfth centuries.

But before this time, there is one incident which may be connected with Knowth and which is worthy of mention. Christianity came to Ireland in the year 432 AD, brought by the now famous St. Patrick, who landed at the Boyne estuary and is said to have made is way to the Hill of Slane where legend tells us he lit Ireland's first Easter fire.

Professor George Eogan has speculated that St. Patrick's first Easter was celebrated not at Slane, but at Brú na Bóinne, and specifically at Knowth. His reasoning is, he says, backed up by archaeological and historical evidence. He says there is no evidence to suggest Slane was an important site at this time, but that Brú na Bóinne was. The possible Easter astronomical significance of the eastern passage adds intrigue to this possibility.


Knowth Sun Pillar
A sun pillar over the Knowth complex in winter.

During the eighth to twelfth centuries, Knowth became the capital of the kingdom of North Brega, and was ruled by a branch of the O'Neill dynasty, who made Cnogba their headquarters.

Physical evidence of Christian settlement at Knowth can be seen in the form of rectangular houses with stone foundations, and a number of stone tunnels, classified as souterrains. These souterrains, which are among the most commonplace monuments in some areas of Ireland, are evidence of another turbulent period in Ireland's history.

Because of their narrow width, low ceilings, and sometimes complicated forms, with false passageways and hidden chambers, it has been suggested that besides being good places to store food and goods, they were also hideouts. The length and winding nature of one of the Knowth souterrains certainly backs up this view. The souterrain which has its opening at the entrance to the eastern passage, has its terminus at the top of the mound.

Such hideouts had very practical uses, especially during the numerous Viking raids which were said to have taken place at Knowth during the ninth and tenth centuries. They would have served as great places to store food, as souterrains can maintain a steady temperature of about 10 degrees celcius all year round.

There was one more phase of activity at Knowth during the Norman period, but by this time much of the significance of Knowth and its passages, kerbstones and art had been lost and forgotten. The Normans built a fortification on the top of Knowth, again reflecting the realisation from the Iron Age that the structure of the mound came in handy for defensive purposes.

Stone Age legacy

Although its chequered and fascinating history is cause for great interest, it is Knowth's Stone Age legacy which remains the most mysterious and intriguing. The huge mound, covering one and a half acres, contains one-quarter of all known megalithic art in western Europe on a total of 300 stones.

Many theories are coming forward about this great treasure of stone carvings, not least the astronomical interpretations of people like Martin Brennan, Philip Stooke, NL Thomas, Charles Scribner, Gillies MacBain and others.

The arcane nature of the many spiral, circular and serpentine forms on the stones of ancient Cnogba is complemented by some very interesting object finds which were made at Knowth.

The most interesting of these finds was a macehead, carved out of solid flint, which was found in the eastern passage in 1982. Painstakingly carved, the macehead was made of a kind of flint which is particular to the Orkney Islands, suggesting a cultural link between the Boyne Valley and Maes Howe in the Neolithic period.

Another stone object, a phallus, was also found. Made of sandstone, it features a number of curved grooves along one face, and three interesting carvings at its base. The object may have been used as a hand-held device for calculating the lunar movements, and some of the engravings on this object are repeated on kerbstones at Knowth.

Although not an object as such, the giant ceremonial stone bowl in the northern recess of the eastern chamber presents a real mystery about how the site was constructed. The huge stone cauldron is too big to be moved in or out of the passage, and so many have concluded that it must have been in situ when construction of the passageway began.

What about the astronomy?

Much of Knowth's astronomical function is being overlooked. An indication of how poorly researched and understood the astronomy is can be gleaned from the fact that many people still believe the sun shines into the eastern and western passages of the monument at sunrise and sunset on the vernal and autumnal equinoxes.

The supposed equinoctial alignment of the passages is not borne out by survey readings carried out by Tom Ray of the Institute for Advanced Studies and his archaeoastronomer colleague Frank Prendergast from Dublin Institute of Technology, which show the passages to be aligned on 85 degrees (east passage) and 259 degrees (west passage). This does not concur with equinoctial alignments, and the survey results led to the dismissal of astronomical alignments by the surveyors in a newspaper article. The Scribner hypothesis (nicely summarised by Gillies MacBain on this page) provides a real answer to a 5,300-year-old mystery.

The value of archaeological investigation at the Boyne Valley sites is hard to measure. On the one hand, archaeology has revealed huge amounts of information about our ancient ancestors, and has given us a great insight into life, people and the landscape which existed thousands of years ago.

On the other hand, some of the sites have been damaged, reconstructed or defaced by archeological methods. At Newgrange, the brilliant white quartz facade has become a symbol of Ireland all over the world. But it is supported by a huge concrete wall, constructed during excavations at the site. Archaeological work at Dowth in the 19th century resulted in extensive damage to the mound. The use of so much concrete and other modern building materials such as putty, steel and styrafoam at Knowth has been criticised. 

It has to be stated that the damage did not begin with archaeology. In earlier times, some sites were damaged during the construction of roads. A stone circle at Cloghalea near Dowth has all but disappeared, while the big cairn of Dowth was damaged twice during the 19th century, once during the construction of a nearby road and also during an excavation by the Royal Irish Academy in 1847, the written records of which no longer exist. The great stone circle around Newgrange, of which only 12 megaliths remain, may have originally contained over 30 members. Some of these stones were reportedly broken up and carried away during road construction in the 1800s.

Agriculture has also taken its toll. A mound east of Newgrange, labelled Site U, was mostly destroyed by the time George Coffey explored the Boyne Valley in the late 19th century. Some of the earthen enclosure structures in the Brú na Bóinne area have also been flattened by successive years of ploughing.

A great deal of debate has been sparked by activity in the Boyne Valley not just over the last 6,000 years, but particularly in the last 40. Archaeology has reached a watershed, and the archaeologists of the future must consider less intrusive and more sensitive methods of exploration. Thankfully this is happening, and the use of remote sensing technology has revealed many hidden features and monuments in the Bend of the Boyne landscape, without the requirement for any digging. Unfortunately though, as our awareness and knowledge of the past increases, the number of sites undamaged by urban development, infrastructural construction, agriculture and archaeology is diminishing.

The time to act is now. At the current rate of destruction and damage, the great work carried out over thousands of years will be wiped out within a couple of generations. What a tragedy that would be.

Sunset from top of Knowth
A view of the sunset from top of Knowth.


Eogan George, "Knowth and the Passage Tombs of Ireland", Thames & Hudson, 1986.
Eogan George, "Prehistoric and early historic culture change at Brugh na Boinne", Proceedings of the Royal Irish Academy Volume 91, C, Number 5, 1991.
O'Kelly Michael, "Newgrange: Archaeology, Art and Legend", Thames & Hudson, 1982.
O'Kelly Michael, "Early Ireland: An Introduction to Irish Prehistory," Cambridge University Press, 1989.
Battersby William, "Knowth: Ten Ages", 1999.
Coffey George, "Newgrange and other incised tumuli in Ireland", 1912 (1977), Blandford Press.
Brennan Martin, "The Stones of Time", Inner Traditions International. (Originally "The Stars and the Stones", Thames & Hudson 1983).
Stooke P.J., "Neolithic Lunar Maps at Knowth and Baltinglass, Ireland," Journal for the History of Astronomy, XXV: 39-55, 1994.
Colgan Paul, "Ancient tomb is 'wrecked' by experts", Sunday Times, October 22, 2000.
"289,000 visitors to Newgrange in 1999", Drogheda Independent, March 2, 2001.
Coldrick Bryn, "Knowth Tour Guide Notes",

The above article is an abridged and edited version of a talk given by Anthony Murphy during Earth Day 2000 in Dublin.

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