island near the northwest entrance to the Bay of Naples, Campania regione, southern Italy. It lies between Ischia Island and Cape Miseno on the mainland, and its highest point reaches 250 feet (76 metres) above sea level. Of volcanic origin, it is made up, with the adjacent Vivara Island, of four extinct craters. Parts of the margins of all four have been destroyed by the sea to form crescent-shaped bays on the east side of the island. The only town, Procida, is on the northeast; its castle is now a prison. The soil of the island is very fertile and supports grapes and citrus fruit; fishing is also carried on. Area 1.45 square miles (3.75 square km). Pop. (2006 est.) mun., 10,652.