Cloughoughter Castle Ruin at Sunset, Lough Oughter, County Cavan, Ireland

An Irish isle ruin

All you need for a river is two banks and a steady flow of water, but that only describes part of this Irish river's 80-mile course. Here at Lough Oughter, the River Erne widens into a broad basin—part of a series of loughs that stretches northward almost to the Atlantic, dotted with islands large and small. This one holding Cloughoughter Castle seems so tiny the ruined fortress might flip it right over. Its battle scars from a 1649 siege still visible, Cloughoughter has been a fave of painters (and, of course, photographers) for centuries.