The Megalithic passage tomb at Newgrange is part of the Boyne Valley complex, which also includes the Knowth and Dowth prehistoric sites.
 The exact use and original purpose of the astronomically aligned Passage Tombs of Ireland has long been debated between  archaeologists and those who see a deeper significance to the stone structures.
 The Irish megalithic passage Tombs at Boyne Valley, Co. Meath, including Newgrange, Knowth & Dowth, were constructed circa 3500 BC, before the Pyramids of Egypt!

At Newgrange, The Winter Solstice illuminates the inner passage and chamber every year. Similarly in the Egyptian Pyramids, the ceremonial inner sanctum was aligned with the Pole star and constellations.
During 1999 a Canadian scientist discovered what may be a prehistoric map of the moon's surface engraved on stone within the inner chamber at Knowth, It was part of a rock carving which was highlighted by the nocturnal lunar light. See the BBC Science Report in the link below!