Nendrum Monastery  Nendrum Monastery was a Christian monastery on Mahee Island in Strangford Lough, County Down, Northern Ireland. Medieval records say it was founded in the 5th century, but this is uncertain. The monastery came to an end at some time between 974 and 1178, but its church served a parish until the site was abandoned in the 15th century. Some remains of the monastery can still be seen. The island monastery of Nendrum was traditionally founded in the 5th century by Mochaoi, after whom Mahee Island is named, although a later date for the foundation has been suggested. Mo Chaoi, like the name of many Irish saints, is a pet name. His proper name was Caolán and according to tradition he was appointed by St. Patrick. However, dendrochronology has dated a tide mill on the island to the year 619, making this the oldest excavated tide mill anywhere in the world. The monastic site included orchards, gardens, pastures, arable fields, and a guest-house. In his "Ecclesiastical Antiquities of Down, Connor, and Dromore", William Reeves notes that several annals record the death of St Mochaoi of Nendrum at a variety of dates between 490 and 497. He considers that Nendrum was early chosen as the seat of a bishop, quoting the "Annals of Tigernach" and the "Annals of Ulster", both of which describe Cronan (died c. 640) as "bishop of Nendrum". There are references to Nendrum in various sources, such as the "Annals of the Four Masters", between the 7th century and the year 974, when the Four Masters record that "Sedna Ua Demain, Abbot of Nendrum, was consumed in his own house". This is read as meaning that Sedna was burnt, perhaps during a Viking raid, and is the last heard of Nendrum in the annals. Reeves says –   The English monks were Benedictines and founded a small cell on Mahee Island. However, in 1306 Nendrum was recorded as a parish church, and during the 15th century it was abandoned for a new site at the village of Tullynakill. The location of Nendrum was then lost until it was rediscovered in 1844 by William Reeves, who visited the island searching for the church recorded in 1306 and recognized the remains of a round tower.