aligned with the Summer Solstice sunrise, such that for some weeks around the summer solstice, sunlight can find its way through to the back wall of the burial chamber. The monument is part of a cluster of Neolithic and Bronze Age features. Two further cairns have been identified just to the south of Bryn Celli Ddu, while in the field immediately to the west is a standing stone, and a rock outcrop with cupmarks carved into it. Original uses The earliest identified remains at the site are a row of five postholes previously thought to have been contemporary with the tomb. Radiocarbon dating of pine charcoal from two of the pits, carried out in 2006, showed these to date from around 4000 BC, putting them at the end of the Mesolithic, 1,000 years before the next phase of use. Their purpose, however, is unknown. Henge In around 3000 BC a henge monument was constructed. An outer circular bank and ditch would have defined the boundary, although only the ditch survives, some across. Within this, a stone circle would have provided the focus for a site of ritual significance. A ring of 17 stones formed an oval, many being in matched pairs either side of the centre. Cremated human remains were buried at the base of some of them, suggesting a central 'altar' During this period a pit was dug within the henge; a single human ear-bone was buried, and covered with a flat slab. A second stone known as 'The Pattern Stone' lay nearby, with the serpentine patterning on it. It is thought this would have stood upright within the henge, as the patterns cover both sides. Passage grave Some 1000 years after the henge was built, the site was radically altered. All but one of the standing stones were intentionally damaged, some were knocked over and six were smashed with heavy stones. In its place a passage grave was built. Much larger than the mound now remaining, it would have had a complete circle of kerbstones following the line of the old henge ditch, creating an impressive retaining wall around the mound, across. The burial chamber would have been entirely enclosed within the mound, rather than the back wall being open to the air, as in the reconstructed mound now seen. Individual human bones, both burnt and unburnt, were found within the chamber and passage, suggesting a variety of