Round tower (20 m high) with round-headed doorway on E side. A plain round-headed window is set high up on the S side of the tower, a gabled window half-way up on the W side, and a flat-topped window high up on the N side. The tower is built of grey limestone (?). To the S of the tower is a small rectangular church, ruined, with some late Gothic details.

Foundation attributed to St Oengus the Culdee (d.815). Monastery first mentioned in 1083. Used as a parish church until at least 1418.

Few round towers in Ireland boast Romanesque detailing, and of these, not all have this detailing around the doorway (for instance at Devenish, Co. Fermanagh, the decoration is around the cornice). In having an ornamented doorway, therefore, Disert Oenghusa tower can be compared to the tower at Kells, Co. Meath, at Dromiskin, Co. Louth, at Kildare, Co. Kildare, and most famously at Timahoe, Co. Laois. While some round tower doorways, such as Timahoe, are composed in an almost identical manner to church doorways, with multiple orders, there seems to have been more disparity and freedom in the way tower doorways were decorated, even at the height of the Romanesque, as shown by the plain doorway of Clonmacnoise round tower, which is historically dated to the mid 12th c. And the round tower at Devenish, whose masons were clearly capable of elaborate architecture sculpture, nevertheless marked the doorway simply with a plain raised continuous moulding. Disert Oenghusa doorway combines an ornamental Romanesque vocabulary with an unwillingness to break the continuinity of the opening, resulting in a unique creative compromise. The use of a row of continuous bosses is best paralleled at Aghowle, Co. Wicklow, where the lintelled west doorway is also ornamented in this manner. This does not suggest a connection, but rather that this was a Romanesque ornament which was easily adapted to older architectural forms. (Ed).