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 very young .