How the people who built Newgrange transported the stones to the spot remains a mystery. The mound above the tomb measures more than 330 feet across and reaches a height of 36 feet. White quartz was used for the retaining wall, and egg-shaped gray stones were studded at intervals. The passage grave may have been the world's earliest solar observatory. It was so carefully constructed that, for five days on and around the winter solstice, the rays of the rising sun still
hit a roof box above the lintel at the entrance to the grave. The rays then shine for about 20 minutes down the main interior passageway to illuminate the burial chamber. The site was restored in 1962 after years of neglect. The geometric designs on some stones at the center of the burial chamber continue to baffle experts. Tours of the site depart from the Brú na Bóinne Visitor Centre.