A passage grave was built in the centre of the henge. The passage is about 8.5m long and 1 m wide. The burial chamber is about 2 m wide, made from six large upright stones, covered with two capstones. A stone, carved with a twisting, serpent like design was in the burial chamber. It has been moved to the National Museum of Wales and replaced with a copy standing outside. The earth barrow covering the grave was made in after the 1928 dig; the original was probably much bigger.