Lying roughly between Avebury and the West Kennet long barrow is a massive conical mound, believed to be some four and a half thousand years old. This 'hill', the largest man-made mound in Europe, has a base circumference of 1630ft (494m), and reaches a height of some 130ft (41m).
Silbury Hill covers an area of five acres and was built as a series of six terraces. Constructed primarily of chalk and soil, each terrace was covered with a layer of loose flint, chalk and gravel to form the current cone shape. The uppermost terrace was left unfilled to form the distinct 'cap' at the top which is still clearly visible on the eastern side of Silbury Hill. During the late 1960s, scientific excavations provided evidence that the hill was built in three separate phases. At completion of phase 1 Silbury Hill was estimated to be 18ft (5m) high, by phase 2 it had tripled in size, and at the end of the third phase it had reached its current height - over eight times larger than when it was first built.
Many theories have been put forward in an effort to understand the original purpose of Silbury Hill, and numerous legends surround it. From various excavations of the site it has been confirmed that nothing was buried at the centre, and the story of King Sel's entombment remains pure legend. However, one explanation that seems plausible is that it provided a means of following solar activity, as shadows were cast from its summit. There is a great deal of evidence for ancient Ley lines that link key sites in this area. Silbury Hill is also at the centre of alignments for straight prehistoric tracks, re-surfaced by the Romans, who may have used the hill as a surveying point. About a thousand years ago, it is known that Saxons occupied the top of the hill.
Despite several attempts to excavate Silbury Hill over the last two hundred years, no concrete evidence has yet been discovered to help solve the mystery of why the mound was first built. Perhaps what is more interesting is the fact that it took some 18 million man-hours to build Silbury Hill in its current form. Nearly three-quarters of the material used had to be quarried with basic implements made from stone, bone or wood, and then carried to the site.
Although factual knowledge of these incredible Neolithic constructions is limited, and their true purpose may never be known, they certainly have a magnetic appeal to modern civilisations. Visitors come from far and wide to stare in wonder, and almost disbelief, that so primitive a people could have achieved such a feat all those thousands of years ago. And even more staggering - why?