Islet of San Juan de Gaztelugatxe (Spain)

San Juan de Gaztelugatxe is a rugged islet in the Bay of Biscay. The Basque word gaztelu means castle and aitz (or atx) means rock, describing the shape of the crag. A hermitage has stood on the summit since the 9th century. In the 12th century it became a convent before the friars moved away, and the site has repeatedly served as a medieval defensive fortress and battle site.