Stonehenge is a 5,000 year-old mystery. Despite years of investigation, archaeologists can't agree about why or how this stunning and mysterious monument was built. Some argue the world famous monument, with its careful alignment to the midwinter solstice, was a giant calendar or observatory. Others insist it was cathedral to some unknown gods. One widely held theory is that Stonehenge had spiritual significance for healing sick pilgrims. But now the discovery and dating of an ancient mass-grave at the Stonehenge site is overturning all of these assumptions and suggesting that this iconic site began as a Neolithic graveyard. Written by Enzedder