The monument includes the ruins of a medieval tower house, which is Listed Grade II, situated in a commanding position on top of crags immediately south of Duddo village. The south west corner and part of the south wall of the tower survive to a height of about 9m and are built of coursed, roughly squared stone. At first floor level is a square window with a chamfered surround and the remains of a second floor window above. At the south west angle a few stones remain of a projecting course that seems to have formed the base of a parapet. Around the base of the standing remains is 19th century masonry, built to prevent its collapse. Large pieces of fallen masonry lie to the south east of the tower and are the remnants of a projecting turret. The outlines of the remaining sides of the tower are difficult to see but measure approximately 12m by 10m. Evidence for the former appearance of the tower has come from late 19th century photographs and a published description by Bates. These describe a tower block with a projecting wing on the south front which contained the entrance and a stair. A barn-like building is also described as having stood near the tower and was removed in about 1850. To the south east of the tower, earthwork remains of building foundations can be seen which are interpreted as remains of the buildings described by Bates. The first known documentary reference to a tower at Duddo was when it was destroyed by James IV of Scotland in 1496. A part of this tower remained standing in 1541 and was described with a barmkin around it in 1561. The present remains are believed to be those of a late 16th century tower.