The Longstones are two huge megaliths situated in a field to the south west of Avebury. They are also known as the Adam and Eve stones. The stone closest to the road is Adam, and is the sole survivor of a cove structure consisting of four stones. The smaller surviving stone is Eve, and is the last remaining stone of Beckhampton Avenue.

Writing in the 18th Century, William Stukeley theorised that West Kennet avenue (the avenue of stones to the south east of Avebury) had originally been mirrored by another avenue on the south west side - Beckhampton Avenue. He speculated that The Longstones were the last remnants of this avenue.

For many years, this theory was considered fanciful in many circles, until he was vindicated by archaeological investigations at the turn of this century. Those investigations uncovered 120 metres of the avenue, revealing socket holes in a double row at intervals of 15 metres - a similar arrangement to West Kennet Avenue. In four instances, buried stones were also revealed.

Although the course of Beckhampton Avenue was only identified as far as The Longstones, it is possible that it extended beyond this point.

The Longstones are usually overlooked by visitors to Avebury, being tucked away some distance from the main tourist circuit of the village. This makes for quite an unusual experience - the opportunity to enjoy two spectacular Avebury stones in peace and solitude.