Remains of a neolithic tomb.
see http://www.kentdowns.org.uk/map_details.asp?siteID=70
see http://www.nationaltrust.org.uk/main/w-global/w-localtoyou/w-south_east/w-south_east-countryside/w-south_east-places-north_kent/w-south_east-places-north_kent-coldrum_longbarrow_wrotham_water.htm
see http://www.megalithic.co.uk/article.php?sid=359