The Portal Tomb of Rathkenny, locally known as the “Druids Altar,” is located in pastureland to the east of Rathkenny House, north of Rathkenny (in Irish, Ráth Cheannaigh) near Nobber in County Meath, Ireland. It is one of only two Portal Tombs in County Meath (the other being the more extensively destroyed Portal Tomb of Ervey). Portal Tombs are megalithic structures found in the British Isles, characterized by two equally tall upright stones with a doorstone in between, forming the front of a chamber covered by a partially massive capstone.
The tomb consists of a large capstone, approximately 3.25 meters long, 2.55 meters wide, and 0.85 meters thick, leaning diagonally on the ground. It leans against the only upright stone, the sole surviving orthostat. The underside of the capstone, estimated to weigh around 20 tons, and the north side of the orthostat are adorned with carved arches and cup-like markings known as “cups.” In his book “The Dolmens of Ireland” (1897), William Copeland Borlase reports on the tomb and cites George Victor Du Noyer’s (1803–1869) descriptions of the rock carvings.