~Ok this is a slight lie. This major centre of Neolithic ritual / settlement activity isn't here any more. It had two concentric rings about 20m apart and was 180m in diameter. I include it because of its current guise - Junction 13 on the M25 at Staines, a curious circular echo of its former self. Kind of depressing but strangely interesting. it makes me think of lovely Mayburgh henge and its narrow escape from the motorway there.
This article, if you can find it, will no doubt have all the details:
Proceedings of the Prehistoric Society
Roberston-Mackay, R. The Neolithic Causewayed Enclosure at Staines, Surrey: Excavations 1961-63. 53, 1987 Page(s)23-128