From the Irish Cill Shléibhe for Mountain Church, this site held one of early Christian Ireland's most important early monastic sites. Founded by St Monnina in the 5th century, the site at the foot of Slieve Gullion is largely restricted to two adjacent churches, a graveyard, the reputed grave of St Monnina's grave, and a small holy well still visited by pilgrims on her feast day, 6 July. The West Church dates from the 11th century. It is the smaller and more ancient of the two with an impressive lintel doorway. The East Church dates from the 15th century and has an impressive arched window with angel carvings still visible.