Marhungbaurg was built on a very gentle rise near the confluence of the Celduin and its tributary, the Ardruiga. To conform with the angles of the land and the junction of the waters, it was given a triangular plan, with each side of equal length. A ditch was dug at the base of the rise and an earthen wall was erected with the fill. Tunnel-gates were cut through the center of each wall, and faced with reddish stone from the river. Wooden bridges provided access to the entries and a wooden pallisade crowned the walls, forming a battlement. At each of the three corners, the Horse-lords built a round bastion (Rh. "buiric") which was level with the walls and contained a rectangular guardhouse.