Silbury Hill rises unexpectedly from the flat valley floor just south of Avebury, a perfectly shaped chalk pyramid that looks too regular to be natural but whose purpose remains completely unknown. It is the largest artificial mound in prehistoric Europe, built in stages over several centuries beginning around 2400 BC, and it aligns precisely with other monuments in the Avebury complex.
Visitors can view the hill from a path around its base, but climbing it is prohibited — repeated excavations and tunnel collapses have made the interior unstable. The hill is best seen from the road between Avebury and West Kennet, where its strange profile against the downland sky is most striking. It is managed by English Heritage and freely visible from public paths.