The history of this monastic house is full of doubts, including the founding date, which is placed in the mid-9th century. Probably in the year 853, bishops Severino and Ariulfo donated this monastery of Yermo to bishop Serrano of Oviedo. In that donation, it was specified that the house had been founded by the bishops themselves with the support of Ramiro I (King of Asturias between 842 and 850). The same donation also included other properties linked to the monastery.
There is practically no information about its development nor extinction. In this regard, the abbot Poncio of Yermo is mentioned in 1031, indicating that the house was still active at that time, but no later records have been found. A Romanesque church is preserved, possibly dating from the late 12th century, when the site likely no longer had a monastic function. The building retains notable sculptural decoration: the southern doorway, slightly pointed, features four capitals, two on each side, and a tympanum depicting a knight fighting a dragon. Some reliefs and a large series of modillions with various figures, including popular characters and others of a prurient nature, are also worth noting.
- GARCÍA GUINEA, Miguel Ángel; dir. (2007). Enciclopedia del Románico en Cantabria. Aguilar de Campoo: Fundación Santa María la Real
- RISCO, Fray Manuel (1789). España Sagrada, tomo 37. Madrid: B. Román
- SERRANO, Luciano (1935). El Obispado de Burgos y Castilla primitiva. Desde el siglo V al XIII. Vol. 1. Madrid: Inst. Valencia de Don Juan
The church is located in the town of Yermo, in the municipality of Cartes, south of Torrelavega