The Monastery of Obona has unclear origins as there are doubts as to the veracity of its founding charter, which attributes its establishment to Adelgaster, son of King Silo, in 871. Other documents certify its existence in the 10th century, and in the 12th century it was an important centre for Benedictine monks. After visiting the monastery, Alfonso IX granted it the charter as a place of mandatory passage for pilgrims on their way to the tomb of St James the Greater in Santiago de Compostela, thereby increasing its economic and cultural control over the area. In its heyday, the monks at the Monastery of Obona applied innovative techniques in farming and livestock breeding, as well as teaching philosophy and theology.
In the 12th century, the Monastery of Obona was an important Benedictine centre, comprising the church, cloister, convent buildings and the hostel. It has undergone numerous alterations, the church being the oldest building.
The Romanesque church dates from the 12th century and has undergone few modifications. It presents a morphology that combines Benedictine architecture with Cistercian aesthetics, based on the lack of decoration and the austere walls. The basilica ground plan is divided into three naves with five bays, finished off with a triple apse, preceded by a straight section, where the main chapel is much larger than the side chapels.
The ceiling of the body of the nave is wooden, while the apses are covered with barrel vaults and cul-de-four. The portal under the eaves at the west end of the church sticks out slightly and consists of four orders of arches supported on eight columns with short shafts, crowned by capitals. A rectangular body above the eaves contains the bell gable with two bells. The side portal is very simple and lacks ornamentation. The apse is polygonal outside and hemispherical inside.
The monastery began to be remodelled in the 17th century. The cloister remained uncompleted. It is divided into two floors with different designs; the ground floor has semi-circular arches with moulded profiles and the upper floor, quadrangular bays separated by elongated pilasters that rise up from the ground floor. The founders of the monastery were buried in the original cloister, although their remains were moved inside the church in the 16th century.
