The monument consists of the round tower at the SW angle of the nave of Brechin Cathedral.
The round tower, with upward tapering walls, rises to a height of about 26.5m, from a base 5m in diameter. It is capped by a later stone spire. Its chief original feature is the carved doorway, which has a crucifixion at its apex, unidentified saints on the jambs and crouching beasts flanking the threshhold.
The tower is now embodied in the SW corner of the cathedral nave, and a doorway (now blocked) has been cut through its wall to give access from the cathedral. However, the tower was almost certainly originally free-standing. A religious community of some sort is known to have been on the site from at least the 970s, though the tower is unlikely to date from much before 1100. The spire is probably of the 15th century.
The area to be scheduled is circular, 5m in diameter, to include the tower and the ground below it, as marked in red on the accompanying map.