Side view of the facade and entrance at Newgrange, a prehistoric passage tomb and ceremonial chamber dating from about 3200 BC. Boyne River Valley, County Meath, Ireland. The facade around the perimeter is made of sparkling white quartz brought from 50 miles away, punctuated by egg-shaped granite stones. The facade has been shaped by archaeologists to allow for visitor access; the dark stones that curve inwards were deliberately chosen to show they are not an original feature of the tomb. Originally, the white facade continued above the round stones, with a narrow recess leading to the entrance. Directly in front of the entrance is the Threshold Stone, which is elaborately carved with spirals, concentric circles and diamond shapes. Their meaning is not known but theories are plentiful. Above the entrance is a "roof box" that allows sunlight to stream in on the winter solstice.