Newgrange, anciently called Síd in Broga and Brug Mac ind Óc, is Ireland’s most famous prehistoric monument.
It was built by a community of farmers and astronomers around 5,200 years ago. Newgrange is best known for the illumination of its passage and chamber by the winter solstice sun. Above the entrance to the passage at Newgrange there is a opening called a roof-box. This baffling orifice held a great surprise for those who unearthed it. Its purpose is to allow sunlight to penetrate the chamber on the shortest days of the year, around December 21st, the winter solstice. At dawn, from December 19th to 23rd, a narrow beam of light penetrates the roof-box and reaches the floor of the chamber, gradually extending to the rear of the chamber.