Nendrum Monastery mill

The Nendrum Monastery mill was a tide mill on an Mahee Island in Strangford Lough (modern Northern Ireland). It is the earliest excavated tide mill, dating from 787 AD. Its millstones are 830mm in diameter and the horizontal wheel is estimated to have developed 7/8HP at its peak. Remains of an earlier mill dated at 619 AD were also found.