Santiago Cathedral of Bilbao was originally built during the 14th-15th centuries as Bilbao's main parish church, and was only declared cathedral in 1950 when the Roman Catholic Diocese of Bilbao was officially created. Its origins probably date to well before the foundation of the city in 1300, when Bilbao was little more than a small enclave of fishermen.
The church is consecrated in honor of the apostle Saint James the Great (Santiago), by virtue of being a point of transit for the pilgrims that followed the Northern branch of the Way of Saint James.
Architecturally, the present building is a mixture of styles: from the 15th century Gothic of the cloister and the main vault, where of special interest are the cloister and the beautiful portal that gives access Correo street (Puerta del Angel), to the ostentatious Gothic Revival façade and spire.
A curious custom is the addition of stone carvings of local merchants along the buttresses of the main vault.
References:The Church of St Donatus name refers to Donatus of Zadar, who began construction on this church in the 9th century and ended it on the northeastern part of the Roman forum. It is the largest Pre-Romanesque building in Croatia.
The beginning of the building of the church was placed to the second half of the 8th century, and it is supposed to have been completed in the 9th century. The Zadar bishop and diplomat Donat (8th and 9th centuries) is credited with the building of the church. He led the representations of the Dalmatian cities to Constantinople and Charles the Great, which is why this church bears slight resemblance to Charlemagne's court chapels, especially the one in Aachen, and also to the Basilica of San Vitale in Ravenna. It belongs to the Pre-Romanesque architectural period.
The circular church, formerly domed, is 27 m high and is characterised by simplicity and technical primitivism.