In any case we know that the arrival of the Cister Reform to Galicia was in the XIIth century (Oia adhered in year 1.185). From here on we leave the doubts, all the documents reveal that the abbey was an economical center of the Miño Valley and surroundings, including Northern Portugal and during some time the great port of Baiona .

The monks of Oia (also called white monks by their habits) turned an unproductive region into a zone of renewed wealth, introducing a big change in agriculture. Their contributions remain today, for example the famous “Curros” with wild horses together with the great wines that we can taste in the region of Miñor Valley.

In addition,the Monastery of Oia constructed roads facilitating the communication between the regions.

They where the ones who defended the coast and the bay; also implementing their religion and culture into the general education in the region.

The Spanish Monarchy gave them the title of Royal and Imperial Monastery of Oia in 1.625 a.C.

The proximity of the Monastery to the ocean is a distinguishing sign of Oia, no other Monastery of the Císter Order is situated so close to the ocean. The small bay in front of the abbey was frequently used like shelter of the boats that sailed out from Baiona.

One of the most famous stories happened in 1625: three Christian vessels, two Portuguese and another French were persecuted by turkish pirates who were looking for treasures. The ships had to take refuge in the bay of Oia, and the monks and a troop of soldiers who lived in the Monastery, were forced to defend the coast.

Besides, we know that in many occasions the aid of the neighbors was also required.

One of the monks who had been a soldier, while shooting he shouted “ In the name of Saint Mary of the Seas”. With this shot he sank the best ship of the pirates.

When king Felipe IV heard about this he congratulated and awarded the performance of the monks and the town of Oia.