Gaztelugatxe, meaning castle rock in Basque language, is a small island on the coast of Biscay. The island is connected to the mainland by a man-made bridge.
On top of the island stands a small monastery named San Juan de Gaztelugatxe, dedicated to John the Baptist, that dates from the 10th century.
The stamp is marking the 75th anniversary of the burning of the city of Santander in 1941. The old city centre was almost completely destroyed by the fire, 10,000 people were made homeless.