The story of Nendrum
Tradition links the founding of Nendrum to St Mochaoi, who died in the late 5th century, and later sources tie the site to St Patrick. By the early medieval period it had grown into a substantial monastery with workshops, a round tower and a church, ringed by its three concentric cashel walls.
On the foreshore below the monastery, monks built a tide mill that was working in the early 7th century, dated by its surviving oak timbers. It is the earliest known tide-powered mill in the world, harnessing the rise and fall of the lough to grind grain.
The annals record that in 974 the abbot of Nendrum, Sedna Ua Demain, was burned in his own house, possibly during a Viking raid. A Benedictine cell was established here in the late 12th century and the site later became a parish church, before being abandoned in the 15th century and forgotten.
The ruins were rediscovered and identified in the 19th century, and the monastery was excavated by H.C. Lawlor in the 1920s. Later underwater archaeology in the 1990s revealed a submerged stone jetty, medieval pottery and the tide mill that made Nendrum internationally important. The site is now in state care and free to visit.