Slieve Gullion - Sliabb gCullinn, the mountain of the steep slope -is the highest mountain in Co Armagh, the centre of a volcanic ring-dyke complex unique in Northern Ireland. On the southern summit of Slieve Gullion is a large stone cairn which covers a Neolithic passage tomb, similar in plan form to Newgrange, and known locally as the 'Calliagh Berra's House'. Located at a height of 573m, it is believed to be the highest surviving passage tomb in Ireland and on a clear day the views are magnificent. North of the cairn is a small lake, known as the 'Calliagh Berra's Lough', reputed to be bottomless. The Calliagh Berra, the hag or witch of Beara: (Co. Cork) , is a common character in Irish folklore, often associated with passage tombs and cairns, eg at Loughcrew, Co Meath, where we find 'The Hag's Chair' and the low mountain, Sliabh na Calliagh.

The circular cairn is 3 Om in diameter and stands over 4m high above the peaty heather banks. It has a retaining kerb of large granite stones and is built, using mainly local stone, to cover an octagonal chamber which is reached along a short passage, 4.5m long: The passage is roofed with stone lintels, and the central chamber, although now partly collapsed, shows very fine stone corbelling similar to that at Newgrange. The earliest written reference to the passage tomb is found in a letter dated 1739, and in 1788 Charlotte Brooke, the author of a book entitled Reliques oJ/fish Poetry (1789), recorded an account of the opening of a chamber by local people who were looking for the 'Calliagh Berra'. Nothing was found apart from fragments of bone and charcoal.

During excavations in 1961 it was discovered that the burial deposits had been badly disturbed by treasure-seekers, but tiny fragments of cremated bone and a few worked flints were found. The excavators also unearthed many interesting structural features and three roughly hollowed basins believed to have been used for burial deposits, one of which was removed to Armagh Museum. Close examination of the stones in the tomb did not reveal any passage tomb-art, which may be explained by the hard nature of the granite. A bulge on the cairn's north side is probably the remains of a small cairn. No finds were recovered, but it may date from the Bronze Age.

A second cairn, which is believed to date from the Bronze Age, (2000BC-500BC) , is on the northern summit of Slieve Gullion. It measures I 3.5m in diameter and stands just over 1m high. A foxhole dug into the centre of the cairn by American soldiers training in the area during the Second World War disturbed the cairn, and this may explain why no central burial cist was found when the site was excavated in 1961. Of the two cists which were found in the cairn, one held remains of burnt bone and fragments of food-vessel pottery.