The large size of the building demonstrate the importance of the city in its surroundings during the Middle Ages.Building work began in the 13th century, but continued for something over a century. This church is in Santander Gothic style. It has three naves with high ogive vaults. Outside, it is dominated by a tower and 2 austere Romanesque doors. Once inside, the tome of the Inquisitor Antonio del Corro is the outstanding feature.