Gaztelugatxe is an islet on the coast of Biscay belonging to the municipality of Bermeo, Basque Country (Spain). It is connected to the mainland by a man-made bridge. On top of the island stands a hermitage, dedicated to John the Baptist, that dates from the 10th century, although discoveries indicate that the date might be the 9th century. With another small neighboring island, Aketze, they form a protected biotope that extends from the town of Bakio until Cape Matxitxako, on the Bay of Biscay.
The best seasons to visit are spring and autumn.