The Cathedral of the Assumption of Our Lady is located in the Spanish city of Santander.

Its structure is mainly Gothic, although it has been subsequently enlarged and refurbished.

It is a historic and monumental complex, built between the late 12th and 14th centuries on the site of the former monastery; it originally served as an abbey, consecrated to Saint Emeterius and Saint Celedonius, known as the Abbey of the Holy Bodies.

The church was built on a hill surrounded by water, where the Roman settlement of Puerto de la Victoria once stood, from the 8th century onwards to keep the relics of the martyrs sacrificed in Calahorra five centuries earlier. Their skulls were brought here by those fleeing the Muslim domination of the Iberian Peninsula.

The construction of the lower floor dates from the early years of the 12th century, shortly after the city was granted its charter.

It was raised to the rank of collegiate church in 1131 by King Alfonso VII, the Emperor, and the reconstruction of the current buildings began on the initiative of Alfonso VIII, after the granting of the charter of Santander in 1187.

The upper part of the building was built between the end of that century and the beginning of the 14th century. On completion, the Gothic cloister was built.

It later received the title of Iglesia Colegial de los Cuerpos Santos (Collegiate Church of the Holy Bodies).

Of particular interest is the main door, built around 1230, where the first coats of arms of the kingdom are carved, showing castles and lions together, after the definitive unification of León and Castile in the time of Fernando III, whose son Sancho was abbot of the site.

The church was extended in the 16th and 17th centuries with the addition of new chapels.

In 1754 the diocese of Santander was created, and the Colegiata de los Cuerpos Santos was transformed into a cathedral by Pope Benedict XIV, as the head of the new bishopric of Santander.