Isla de San Simón sits in the Ría de Vigo, about 20 km south of Pontevedra, reachable by boat from Cesantes or Redondela. The island is small, wooded, and beautiful — a lush contrast to the industrial fringes of the ría around it. A ruined monastery occupies the southern part, a 19th-century prison building stands at the centre, and forest paths connect them.
The island has a long and troubled history. It was a Franciscan monastery, then a quarantine station for plague ships, then a prison, and finally — most darkly — a detention camp for Republican prisoners after the Spanish Civil War. Today it functions as a cultural venue run by the Xunta de Galicia, hosting concerts and exhibitions. Access is by free boat from Cesantes; check the Xunta's website for schedules, as the island is sometimes closed for events.