Romanesque from the 13th century. Together with the hermitage and the remains of other buildings, it stands on a hill overlooking the River Ebro, protecting the lands of La Sonsierra and La Rioja Alta from attacks from Navarre.
It is made of ashlar, reinforced at the corners with round cubes, giving rise to a seven-sided polygonal shape, of which the square-shaped Torre del Homenaje (Homage Tower) forms part at the eastern end, attached to the wall and housing the chapel on the ground floor.
In the inner courtyard of the fortress there are corbels and grooves that point to the existence of storerooms, stables and other complementary constructions.
In this place where the castle and the chapel are located, there used to be a small village called Davalillo.
In the 18th century, Alfonso X donated the place of San Asensio to Davalillo, and Davalillo became a village of some importance. As early as 1515, the town was already growing.
After the war between Pedro I “The Cruel” and Enrique II, with the fragmentation of La Rioja into seigniories, the decline of Davalillo began, which increased with the struggles between the lords of the castle and the lords of the town, thus increasing the population of San Asensio.