It is the best preserved passage tomb in Europe, and is 500 years older than the Pyramids (3000 b.c. ). It's a huge stone mound (nearly 12 m/40 ft high and almost 90 m/300 ft wide) constructed from 200,000 tons of stone, much of which was somehow hauled from the Wicklow Mountains and the Mountains of Mourne.
The tomb is even older than the Pyramids.