Historical records from the 11th century make reference to a castle that once stood on the site of the current building; a hill that soars to a height of 673 metres. People have come to this spot for centuries in order to worship the image of the Virgin Mary who is said to have appeared to a shepherd called Balandrán above a nearby almond tree.

The monastery is made up of buildings from different eras and typologies. The oldest are the cloister and the church, which date back to the 13th century.

The medieval church was built in the centre of a raised area, atop a rocky prominence, and was made with sandstone taken from a quarry on the same hill. The oldest part is the nave, which is made up of five sections separated by thick, pointed arches that are square in appearance. The central elements of the vaults, the keystones, are decorated with the stripes of Aragon, the crest of Barbastro and the almond tree, above which the Virgin Mary is said to have appeared.

A huge iron grill separates the nave from the east end of the church. This part was originally flat but was substituted by a polygonal structure in the 17th century. It is covered with a hemispheric dome supported by pendentives, which boast the crest of the bishop, Alonso de Requeséns, who sponsored the work. There are only scant remains of the paintings that once decorated the dome, which were painted by Diego Gutiérrez in 1786.

With the aim of satisfying the needs of fervent congregations who wished to worship the image of Our Lady up close, a small chapel was built behind the altar in the 18th century. Entrance was gained through narrow passageways that led from the presbytery.

The interior of the chapel was decorated with paintings and the ceiling was covered with scenes of the life of the Virgin Mary - the Visitation, the Annunciation, the Nativity and the Epiphany - as well as number of angels. The cardinal virtues are depicted on the chamfers:

Strength is depicted as a strong woman dressed as a warrior, armed and wearing a helmet.
Justice is shown as a pair of scales, the symbol of equality, and a sword, an emblem of strength, with which decisions should be made.
Temperance reveals pitchers of cold water to cool burning irons. Prudence is depicted as a mirror, a symbol of reflection and of self awareness, and a snake, evoking the phrase of St Matthew “Be ye therefore wise as serpents and harmless as doves.” (Matthew 10, Chapter 16)

The Gothic sepulchre of San Balandrán stands in a small room attached to the church. He was a man of great stature and tradition says that Barbastro’s young people must be able to touch the ends of the sepulchre with their extended arms before entertaining aspirations of marriage.