Small ruined rectangular church with a reused Romanesque W doorway, a plain Romanesque window at the W end of the S wall of the nave, and Gothic windows at the E end of the S wall and in the E wall.

The site was reputedly founded by St Carthach who formed a community of 867 monks. The deaths of three coarbs are mentioned at the site during the 12th century.

The church was evidently built or rebuilt using spolia from an older church on the site. The fabric contains a large number of well-worked square stones, possibly from the chancel roof of St Carthage's, together with the fragmentary remains of the W doorway. The placement of the label over the outer order is similar to the arrangement in the W doorway and chancel arch of the Nuns' Church, Clonmacnoise, Co. Offaly . Like the reset circular window in St Carthage's the doorway is stylistically related to work at the Nuns' Church, Clonmacnoise, and can probably be dated to c.1160.