The following is also interesting -

The souls of Silbury Hill are bared in burial mound dig

"Researchers have long been mystified as to why the giant prehistoric mound in Wiltshire was built. But following one of the UK's most extensive and expensive digs, they appear to have found their answer: Silbury Hill may well have been a tomb, not for bodies, but for the souls of the dead.

"The English Heritage dig, which cost £1m, tunnelled 85 metres into the 40-metre-high man-made hill, discovering that its Neolithic builders had incorporated hundreds of heavy sarsen stones into its matrix. Sarsen, the silicified sandstone still found in great quantities in Wiltshire, was also used to build Stonehenge and Avebury. Heavier than other types of stone, archaeologists have long suspected that the material was regarded as sacred by Neolithic man.

"Stones have been seen by many cultures as spiritually and physically interchangeable with humans – with a belief that particular stones contained the souls, spirits or even the transformed mortal remains of the dead. The belief was widespread, occurring all over the world.

"Silbury Hill, researchers believe, could well have been built as a sort of spiritual tomb, filled with spirits rather than skeletons."*

The article also suggests that the original the summit, "...had a rounded rather than flat top and was five to seven metres higher than today..." Also that, "...Silbury was associated with a form of river-related religious cult. Until the 19th century, the linkage between the Kennet river and Silbury was reflected by an annual local ritual in which water was collected from the main source of the river – the Swallowhead Spring..."

* http://news.independent.co.uk/uk/this_britain/article3093799.ece