Immediately outside the W wall Traill broke into a subterranean passage which he followed N then NW for some 10m, passing several sets of door-checks and a side-chamber and entering a 'circular building'. Finds from this structure, including a stone ball, are in NMAS (...); others are in Tankerness House Museum (...). The opening into the passage is now blocked by rubble; it is likely that this was part of a complex of late Iron Age buildings, on the wreckage of which the chapel was built. It is possible that that a broch lies at the core of the mound, on the lower SE slope of which a revetment-wall, 1.9m high and traceable for 11m, may be part of an outer wall or ringwork. A few metres to the N of the chapel are the footings of two small subrectangular buildings of indeterminate date. A cross-slab is said to have been seen some years ago in the deep water besides the islet, but an attempted recovery was unsuccessful