Carrowmore is the largest megalithic cemetery in Ireland and amongst the oldest in Europe. It is believed that there may have been over 100 monuments on this site but only 30 have survived as the area was extensively damaged in the early nineteenth century by land clearance and quarrying. On site are the remains of chamber tombs, portal tombs (dolmens), ring forts, cairns and passage graves and each one is known by numbers assigned to them in 1837 by George Petrie, the famous Irish antiquarian and archaeologist. Excavations by Swedish archaeologists in 1977 produced radio-carbon dates that have placed some of the tombs as early as 4600 b.c! A large area of the cemetery is now under state protection and a restored cottage on-site houses an exhibition.