CASTLES ERRENTERIA

Fuerte de San Marcos, constructed in 1888 during the reign of Maria Cristina on Mount Bizarain, was built as a strategic military defense against potential Carlist attack. Designed by Luis Nieva and standing at 260 meters elevation, this fortress formed part of the "Campo fortificado del Oyarzun" fortification plan protecting the coast around Donostia-San Sebastián. Together with nearby Fort Guadalupe and Txoritokieta, it provided crucial defense for the Bay of Pasaia and surrounding lands. Occupied by the Spanish Army until 1970, the fortress now forms part of the Lau Haizeta nature park and houses a tourist information center featuring replica cannons and panoramic views of the Bay of La Concha and Txingudi.

Fuerte de Txoritokieta is a polygonal fort located on a mountain between Rentería and Astigarraga in Guipúzcoa, Spain. Designed by military engineer Luis Nieva and inaugurated in 1890, it features three barbette batteries arranged in a cruciform structure with artillery placements separated by traverses. Built as part of the Oyarzun Entrenched Field to protect strategic positions and cover the Port of Pasajes, the fort suffered naval bombardment during the Spanish Civil War. Today it remains largely abandoned with minimal maintenance, though its architectural design remains evident in the distinctive mountain-top structure.