It is a strategic place for dominating the coast. In fact, Gaztelugatxe was for centuries the scene of battles between the Lord of Biscay and the King of Castille, of acts of plundering and looting by buccaneers and pirates. Also, witchcraft and covens found a haven in Gaztelugatxe.
The hermitage crowning this small island was founded in the 10th century under the name of St. John the Baptist and was a convent of friars for two centuries (12th-14th century). But it declined over the years until it was finally demolished in 1886 and completely rebuilt.
There is a LEGEND about this place that recounts that St. John, after disembarking in Bermeo in three steps that left a mark on the way, arrived at the hermitage. The first mark is located below the “San Juan” arch in the city of Bermeo itself. The second mark is located in the Arene neighbourhood, next to Itsasalde country house, just before the fountain. The third mark is located upon arriving at the final access step to the hermitage. This mark is also the most interesting because in addition to being able to see the mark, we can also read the inscription “SAN JUAN” that someone wrote with a chisel.
At the San Juan Festival on 24th June, a TRADITIONAL PROCESSION is held, where crowds from the vicinity, especially Bermeo, arrive in a pilgrimage on foot at the hermitage to fulfill promises made or to give thanks to the saint. A floral offering is made to the image of the Virgin, immersed in the depths of the sea under one of the natural arches that emerge at the foot of this fantastic island.
San Juan Degollado (29th August) is another festival very much celebrated at the hermitage.
There is a tradition in which, at the start of the Spanish white tuna fishing season, the fishermen and womenfolk usually go to Gaztelugatxe to ask for health, good weather and good fishing. The ritual of asking is also made from the sea. This is why the sailors/fishermen take their boats to the vicinity of Gaztelugatxe to “do what has to be done: three turns to port and three to starboard.”