The huge earth barrow survives to a maximum height of 10.5 feet (3.2 metres) and tapers out from the narrower western end to a maximum width of 82 feet (25 metres) towards the eastern entrance.
At just over 328 feet (100 metres), the barrow is second only to the nearby East Kennet Barrow in length. Although it is now covered with turf it would originally have had bare chalk sides and would have stood out against the landscape. It consists of a core of sarsen stones capped with chalk rubble from the surrounding quarry ditches.
At the eastern end of the mound is an impressive structure consisting of five chambers opening off a central passage. This is fronted by a semicircular forecourt with a façade of huge sarsen stones aligned north–south.
The main passage penetrates about 42 feet (13 metres) into the barrow, with two of the burial chambers on each side of the passageway and one chamber at the end. The side ditches to the north and south of the mound have now been almost buried by ploughing.
It is possible to enter the chamber of the barrow, and from the top of the mound there are good views of Silbury Hill, the East Kennet Barrow, the Sanctuary and Windmill Hill.