The parish church of San Sebastián, dating from the beginning of the 12th century, is Romanesque in style. The tower, part of the arch of the entrance door and a biforia window remain from its primitive structure; and inside, the apse-shaped presbytery; completely renovated with a window in the headwall and a cornice of dadoes around its perimeter.

Also interesting is the doorway with three plain arches, the central one resting on columns with simple Corinthian capitals. There is also a beautiful Christ hanging over the Romanesque altar. It is the first burial place of the Blessed Juana de Aza, mother of Santo Domingo de Guzmán. Saint Dominic was baptised in the small baptistery. The baptismal font was transferred by Alfonso X to the nuns’ monastery for safekeeping until 1605. It is currently housed in the Monastery of the Dominican Mothers of Santo Domingo el Real, in Madrid, where members of the Spanish Royal Family are still baptised.