Medieval chapel. The site was investigated by the Manx Archaeological Survey in 1908. It lies on a slight terrace within a steep cleft on the west side of a hill: the name means 'the hollow of the chapel'.


The Survey found the chapel to be orientated east-west, with the door in the west gable. The structure measures 4 by 2.6m internally. The walls stand to a maximum height of 1.2m, but lean inwards as a consequence of the weight of collapsed material bearing on them outside. Removal of some of this material has revealed that the walls were strengthened historically, increasing their thickness to between 1 and 1.3m.


The cills of the east window and the south window (close to the east end of the south wall) were recognised, and the fallen head of the east window was found when clearing rubble to reveal the base of the altar. The latter measures 1 by 0.6m and 0.3m high. A socket stone and lintel for the doorway were also discovered.


A number of cross slabs have been found incorporated into the masonry of the chapel and in collapsed material derived from it. Though all are relatively simple gravemarkers, Lag ny Keeilley is, after Maughold, the most productive site for such medieval crosses on the Island.