The 130-foot Silbury Hill with nine triangular sides and 36 Meg Yard platform sized as Stonehenge

PICTURE 1. The prehistoric, 130 foot high, man-made Silbury Hill. 10 miles south of Swindon, 5-miles west of Marlborough.


I took an interest in what was going on in prehistoric Wiltshire, and especially Avebury, when surfing the Internet and was amazed to discover that people of some 4,400 years ago had raised a pyramid-size hill with little more than their bare hands. One of my work colleagues had visited this mini-mountain while on a day’s outing from London, when he also climbed up it: something you are not allowed to do today. He also visited the quarter-mile diameter Avebury henge, a stone's throw north of this enigmatic hill. 

I just had to see this mystery hill and henge, the purpose, or purposes of which, no one, including archaeologists, could seem to solve.

And so it came about that on a particularly fine summer’s day in 2001 that I set out with my dad, (who complained the whole way why anyone should want to visit such old relics) to see if I could learn anything to help solve the purpose of these things.

So there we were, dad and I, looking up at the largest man-made mound in Europe; not believing it could possibly have been built for no reason whatsoever. I felt very much challenged, to say the least: no bunch of half-shod barbarians was going to get the better of me: I wasn't brought up to give in so easily.



 2. Silbury Hill is thought to have been started around 2650 BC and completed by 2400 BC, when it probably took over from a failed Stonehenge. Now, I don't wish to get too tangled up with Stonehenge at this point in time because this site is essentially about Avebury. But it seems almost certain that by 2400 BC, Stonehenge was most likely to have been deemed a failure by its builders and, whether or not Stonehenge was ever finished, some of its stones were maybe smashed to pieces and taken back where they came from. If so, some of those fragments were placed inside Silbury Hill as dedications. Quoting Magnus Magnusson... 'The sarsen stones inside Silbury Hill are like currants in a cake.' To this we can add some Welsh bluestone found near the top by Atkinson; bluestones which were lost for a while but later found as part of the Keiller collection in Avebury's museum.

The platform on top of Silbury measures 36 megalithic yards (All measurements on this site are in megalithic yards, unless otherwise stated). The platform at 36 MY, is the same diameter as Stonehenge. That is a well-known fact. And perhaps the nine triangles that travel down Silbury's sides are  meant to represent sunrays spreading out from the centre of Stonehenge. Everything here fits the Stone Age hypothesis - a hypothesis that we will deal with as we go along. 


Silbury Hill started its life as a 120-foot diameter henge with a 20-foot-deep ditch that went down below the water table. In the centre of the henge and standing some 18 feet high was an eclectic pile of soil brought to the site by people coming from many different parts of the country. Atkinson 1968-9. Later, and as Silbury grew in size, note the word grew, a much larger ditch was dug, some 350 feet in diameter, and also 20 feet deep. Every bit of this work is now hidden from view.

Returning to the subject of Avebury...

After spending twenty minutes or so viewing Silbury Hill and taking several photographs of it, we returned to our car and drove the short distance to take a look at the henge at Avebury. Easily large enough to hold a village with a pub, some shops, several dwellings and a small chapel in the centre, I was immediately stunned by the enormity of it all. This so-called “Super henge,” a quarter of a mile across, contains standing stones 'orthostats' even larger than those at Stonehenge. Something big had been going on here - and for an equally big reason. I determined there and then, to find out exactly what that reason was!

Although dad was normally tee-total, he waited with a half of shandy in the car park of the Red Lion public house while I investigated the henge. When at last I returned to dad, I said that I reckoned Stone Age people had been trying to catch the Sun.

And so started my quest to prove it.

Dad and I next paid a visit to the Alexander Keiller museum to see the exhibits and to purchase some books so I could study these things later and in the quiet of my own home. From those books I learned that the egg-shaped monument on top of Windmill Hill was the first to be built; and because it overlooks both Silbury and Avebury; it seemed like a good place for me to start.

Avebury Landscape with Silbury, Windmill Hill, Sanctuary, West Kennet Avenue, Long and round barrows

3. The Avebury Landscape. My model of Avebury and its surrounding monuments, should help you to find your way around.

And so it was that a couple of weeks later, and after purchasing a second-hand single-lens-reflex-camera, that I could be seen heading back to Avebury in the middle of the night to see what all the fuss was about. I was totally convinced that I could solve these age-old mysteries.

Never having been to Windmill Hill before, and without knowing exactly how to get there, and in the middle of the night, to-boot…I duly set out from home. I knew I would have to go up a dark and lonely country lane which leads on to a country track that would eventually peter out; and it's there I parked my car.

It was pitch black when I arrived and I was in the middle of nowhere. I thought perhaps I should wait for the sky to lighten up a tad before leaving my car to walk the rest of the way, but that would only defeat the object.  I somehow managed to pluck up enough courage to set off up that spooky track; after all; should anyone or anything jump out at me, I could always give them, or it, a hefty whack with my torch.

Having parked my car on what seemed likely to be someone's prohibited land, I did not want to flash my torch for any longer than was necessary to ensure my safe footing. Suddenly, I saw a flash of light coming from some distance up-ahead - did I imagine it? - surely not. Am I heading into danger of some kind? I walked on. There it was again. This time I was sure the light was coming from another torch. Too late to turn back now, I had no choice but to see just what it was that I was walking into. 

As I approached still closer I could see that several vehicles had been driven farther up the track than me, and that I was rapidly entering a “New Age traveller’s camp” who thought me a colleague who had come to join them. Why on earth they were still awake at four o'clock in the morning I shall never know; but I bade them good morning and asked for directions. A young lady, who pointed the way, explained that I didn’t have much farther to go, ‘it’s up there, through the gate and at the top of the rise,’ she replied. 

to be continued.

A view of Windmill Hill and wrongly named Adam and Eve Long-stones, part of the Beckhampton avenue

 4. Windmill Hill, with its Bronze Age round barrows on top and seen on the horizon, is framed by the "Longstone's" Adam and Eve.

The archaeologist and author, Aubrey Burl, like Stuart Piggott and Alexander Keiller before him, believed that Avebury’s stones were sexed… “Adam like Eve, surely wrongly sexed, was the eastern side-slab of a south-west facing cove.” A Guide to the Stone Circles of Britain, Ireland and Brittany by Aubrey Burl. p 86

Since I agree with Burl, Piggott and Keiller, and now Dr Terence Meaden too. that many of Avebury's stones are sexed, we will correct this mix-up by naming this pair properly. 

The slim pillar on the right, if correctly-named, ought to be called Adam. This pillar has been proved to be part of Avebury’s long-lost Beckhampton Avenue and is not, therefore, part of the cove. 

The lozenge shaped-stone, which we will call Eve, was one of a pair of side-slabs to the Beckhampton Cove. Eve fell many years ago and was restored to the vertical by Maud Cunnington when she discovered beaker pottery and a burial at its base. The Beckhampton Cove consisted of four stones, three of which opened to the southeast, not the southwest as Burl thought. Eve is the one remaining stone of this cove.


Although they were a catastrophic failure, Avebury’s coves were mankind’s earliest known attempts at producing infinity loops. 

There are several kinds of infinity loops: a short length of magnetic tape, spliced to make a circle, which plays the same piece of music over and over again: A mini code that causes a computer to crash by repeating the same instruction: An infinity loop between Google’s Assistant and Amazon’s Alexa caused a conversation between them that went on ad-infinitum.

Avebury’s infinity loops were coves with pairs of stone mirrors set in parallel.

Infinity loops are brought to an end by the external force that initiated them: The tape, by switching off the recorder: The computer by removing the offensive code: The repeating conversation between Alexa and Assistant by fresh instruction from the loudspeaker that set them off in the first place. 

The initiator of Avebury’s coves was of course meant to be the sun. And perhaps to a lesser extent, light from the moon too. 

LASERS (Correctly capitalised) have parallel mirrors which concentrate and amplify light by bouncing it around. But there is one big difference. One of those mirrors is less than perfect and this allows some bounced light to escape. And, LASERS are also excited and terminated by an external source (of light). 

We will hear more about LASERS and coves, and Stonehenge, as we go along.


The 350-metre causewayed enclosure on top of Windmill Hill, dated 3,450 BC, poses archaeologists as much a mystery as does Avebury and Silbury Hill, or so they say, because although it appears to have been an encampment of some kind, early folk are known to have never lived permanently upon it.

Archaeologists believe that Neolithic people occupied this hill during the summer months only, and then perhaps for nothing more than butchery, so all sorts of theories have been advanced for its possible use - none of which are very convincing.

Causewayed enclosures and long barrows are among the earliest monuments of all, their perimeters marked out by several rings of discontinuous ditches and banks that someone once described as being like a string of badly-made sausages. Well, Windmill Hill is not a sausage, but probably based on an egg. It is, however, very unfortunate that other causewayed enclosures are not egg-shaped at all; although some of them are; but their varied outlines allow for any number of disagreements about their true purpose. What we do know about Windmill Hill is that many things were placed on the bottom of its two-metre-deep ditches. These “things” ranged from stones brought from a quarry near to the town of Bath, (Limestone, no doubt) and other stones coming from as far away as Cornwall - as well as small chips of - surprise, surprise - the famous Stonehenge bluestones having come all the way from West Wales. Its builders may even have brought the honey-coloured Grand Pressigny flint from France.

Besides these exotic stones, animal and human body-parts were also found at the bottom of its ditches, together with the possible sacrifice of a couple of children - not that it’s accepted as fact, mind you. One child was found on a raised plinth that raised its tiny body off the bottom of the ditch, and he or she was probably buried for the same purpose or reason as the single burials found at Avebury’s Sanctuary and Woodhenge (near Stonehenge). This truly eclectic mixture of creature and human remains, exotic stones, flint arrow-heads, axes and broken pottery sherds, was clearly trying to instil the massive geometric egg on top of Windmill Hill with life. For myself, though, I wanted to look south from this enclosure as people of the Neolithic did, to see just what it was that they saw in the place.


Dawn hadn't quite broke when I arrived on top of Windmill Hill, and this gave me time to look around. I have to say that it didn’t look much like the photographs Cambridge University had taken of it from the air, and the Bronze Age burial mounds, known as ‘round barrows,’ came as a complete surprise since I hadn't expected them to be there. Even more surprising was a tent pitched hidden from view between two of  the barrows by someone who advertised with a banner to have travelled all the way from somewhere inside Europe to get there - Bavaria I think - if my memory serves me correctly.

Although the Summer Solstice had passed by some weeks ago, I had come to Windmill Hill to watch the sunrise in the hope that I too might see what Stone Age people had seen in the place. I stood irreverently on top of the largest round barrow and looked towards the south. I hadn't chosen a very good day, but suddenly, there she was, ‘The Lady Silhouette.’

A view of Silbury Hill as seen from on top of Windmill Hill.

5. The 'Lady Silhouette seen from the top of Windmill Hill

This, I thought, was it: this was the way in which Stone Age men and women had tried to catch the sun…a giant image of a woman lying down, formed by the combination of Waden and Silbury Hill together. Obviously, or so I thought, those early guys and gals had built a female breast to go with the Waden Hill belly. I was sure that I had cracked the mystery; so sure, in fact, that I just had to write a story about it. I didn't know it at the time, but this beautiful idea was to become just one further theory that I would eventually come to drop.

Besides which, I was looking in the wrong direction!

The outer circuit of Windmill Hill as a vast geometric exercise based on Alexander Keillers plan.

6. Windmill Hill's outer circuit as a vast Geometric exercise. 

Unless otherwise stated, all dimensions on this site and its sister site,, are in Professor Alexander Thom's megalithic yards. One megalithic yard has been shown to equal 0.83 of todays metres.

No wonder Windmill Hill was such a popular place to be 5,300 years ago; people used it as a vast experiment in geometry and mensuration. This geometry would one day lead to the setting out of Avebury's outer ring of some 90-plus orthostats. Note how by doubling in size at each step, these circles suggest growth.

Windmill Hill Ring B as a vast geometric exercise based on Alexander Keiller's plan

7. Windmill Hill Geometry, Ring B. 

Ring B appears to be composed of at least four 187.5 arcs from four 375 diameter circles. 375 times 4 gives 1500, again equalling Avebury's largest diameter.   

Windmill Hill using Cherhill Hill as an observatory for tracking the winter solstice.

8. Cherhill Hill, seen from Windmill Hill. A round barrow and its ditch can also be seen in this picture. 

If Windmill Hill's two outer circuits can be thought of as based on egg-shapes with axes passing centrally through them, then the monument used the distant ridge of Cherhill Hill to track the comings of the winter solstice sun.

A CAD version of the Avebury henge, showing positions of its circles, ditches and banks.

9. Avebury Henge. This CAD version of the Avebury Henge, which I produced some years ago, is the best I can do to show you what the Avebury Henge looked like when new. The whole complex is about a quarter of a mile diameter. The internal ditch, some 20 feet deep, followed the contours of Avebury's outer circuit of standing stones. Some stones of the outer ring were found to be held in place by having lower chalk rammed hard against their bases. We don't know where that lower chalk came from, but it wasn't from the bottom of Avebury's ditch - that was far to easy and uncharacteristic for the Stone Age. Silbury's ditch, known to have been dug around 2,650 BC, makes a good candidate for that chalk may have come from.

My CAD view of  Avebury looks roughly east, so the south exit causeway, not an entrance, is on the left of the picture. The double row of stones known as the West Kennet Avenue can be seen leaving the henge via this causeway. The WKA is on its way to the Sanctuary.

The Beckhampton Avenue of paired stones that William Stukeley claims to have existed, can be seen leaving the henge via the east exit. The existence of the Beckhampton Avenue was disputed and argued over for many years before archaeologists finally found a stone or two along its route. Personally, I'd be a lot happier had they found a few more.

The inner circle on the left is known as the Southern Circle. Alexander Thom claimed this circle to measure 125 megalithic yards diameter; as well it might do if measured through the centre of the stones. However, since the best faces of its stones point inwards, the Southern Circle actually measures 123 MY internally.

The stone setting inside the Southern Circle has always been known as the Z-feature, but recent work on the Z feature suggests it to be a rectangle. I am not privy to this work and must wait for further information about it. 

The inner circle, seen on the right, is actually egg-shaped. The remains of a cove stand in the middle of this egg.

The exit causeway on the right leads to Swindon.


The causeway in the foreground leads to the Marlborough Downs from where early folk fetched their treasured sarsen stones.


A picture of Avebury's, previously undiscovered, founding geometry

10 and 11..  The undiscovered founding geometry of Avebury's outer ring of stone orthostats. 

Stage 1 Draw a 3:4:5 Pythagorean triangle A, B, C as seen on the left above, and make it 75 by 100 by 125 megalithic yards. 

From a point 15 over and 42 up from corner A, construct a second 3:4:5 Pythagorean triangle, but this time make it 10-times size at 30, 40 and 50 MY. We will cast a 250 MY radius from corner F of this second triangle - but hold on a moment…

Stage 2 We hold back because we can add a third 3 : 4 : 5 Pythagorean triangle as further support when casting our 250 radius. This third triangle is 11.333-times-size 3:4:5, and has sides of 34, 45.333 and 56.666 re-occurring.

The shear simplicity of this geometry, founded on a family of three of the most basic of Pythagorean triangles, made early folk believe they had discovered something of immense importance and was sufficient reason for basing Avebury upon it. We also note how several more 3:4:5 triangles can be added to this design, but these extras are not needed. 


Fact: Avebury, like Stonehenge, is an internal device. If you heard it any other way, then you heard wrong.

Avebury's outer circuit Stage 3.  Casting a 200 and a 250 megalithic yard arc from points D and F

12.  We now cast a 250 radius from point F. We also take the opportunity to throw Professor Thom’s 200-radius circle from our point D. (It is a mere tenth of a megalithic yard different to Thom's). Only a portion of these arcs are needed and shown.

A temporary section of the 200 MY arc, shown doted, has been allowed to remain for clarity. This will be removed in the next stage.  

Avebury outer circuit Stage 4. Producing a 750 megalithic yard arc, 200 megalithic yards from D

13. Avebury folk then threw a 750 radius from a post 550 megalithic yards from D. Well, that’s the theory! Perhaps this 750 radius was prototyped on top of Windmill Hill, as we suggested above, but perhaps it was somewhere else? Maybe some of that scaled-down geometry lies buried beneath Silbury Hill. 

But the question is, how did early folk produce such a large 750 radius arc using only wooden pegs and stretchy ropes?

Avebury Henge, describing how the 750 megalithic yard radius arc may have been achieved.

14 (left) From the above, we can see that a cord, 244 megalithic yards long, when stretched across a 750-radius circle, stands off the arc by 10 megalithic yards. Scaling down ten times is therefore not difficult to do. Ten megalithic yards becomes one, and the 244 cord becomes 24.4. And; since we only need deal with half- arcs at a time, 24.4 reduces to 12.2.

15 (right) Few coordinates are needed to produce a reasonably good 750MY arc. After running a rope around as few as six pegs, like those represented above by tiny black dots, the curve would be easy to improve by eye.


Fact: Professor Thom used Avebury's great size to refine his megalithic yard to 32.664 imperial inches. What is less known is that he measured to the inside faces of Avebury's stones. Clearly then, Thom also understood Avebury to be an internal device!  

Avebury stages 6 and 7. The geometry of Avebury's outer ring of stone orthostats made complete.

16. Avebury's geometry, stage 6.

Again following the work of Professor Thom, three 260-radius arcs are now cast from A, B and C of the initial triangle. This leaves only one more arc to go.  

Fact: The most important Stone Age number is the number three because it represents the family. This has been known since 2008 when this author noticed that some timber posts of Durrington Walls' Southern Circle (its an egg!) were set up in rows of three.

Aubrey Burl also noticed how people itemised things in three’s in his book “Prehistoric Avebury,” page 117, 1979.

It also follows that as well as founding Avebury on three triangles, the 750 arc should be three times greater than the 250 arc. This eye-opening geometry, based on the simplest of Pythagorean triangles, was the motive that spurred Avebury folk to action.

17. Avebury's Geometry, Stage 7. 

Professor Thom made the second 750 megalithic yard arc convex to match the others. But recent results of ground penetrating radar conducted by the Ordinance Survey suggest this final arc might be concave as I have drawn it. However, the exact geometry in this particular sector can only be resolved by further excavation. Please press the red Find out more button above.