Nendrum is a fifth century Monastery, now only ruins, on Mahee Island in County Down, Northern Ireland. The ruins include old walls, graves, the stump of a round tower and of a church with its sundial. It was founded by Mochaoi and was probably pillaged and destroyed in a raid by the Danes in the tenth century. The sundial, shown here, is partially a reconstruction, and is one of the few medieval sundials in existence. Mahee Island, the site of the monastery, is on the west side of Strangford Lough in County Down, Northern Ireland and is reached by a narrow causeway that passes the ruins of Mahee Castle.