Man-made underground passage in Márthain

Man-made underground passage described by Cuppage (1986, 170-71, no. 504) as follows; 'A substantial univallate rath [KE042-131----] containing traces of possible hut-sites [KE042-131001-] and a possible Man-made underground passage. It abuts the W side of a roadway on the E slopes of Croaghmarhin. Much of the N portion of the interior is occupied by irregular ridges and hollows, the mounds being composed chiefly of stone. They do not conform to any recognisable pattern but some linear hollows may indicate a Man-made underground passage and some large prostrate slabs in the vicinity may be related to this. The largest mound measures 5.05m E-W and is up to 1.2m high. It may be the remains of the structure described by O'Sullivan (1931, 520) as 'a rectangular stone structure about 4 feet high, roofed with flags, one of which has fallen in.'