The entrance facade bears a curious 14th century inscription dedicating the building both to the martyred brothers and to "the black and beautiful Virgin". Above the inscription, the martyred brothers are shown kneeling on either side of the Virgin and Child.

This is one of the oldest churches in Barcelona and is dedicated to the two martyrs, Justo and Pastor, who were the subjects of veneration during the 4th century. The building is documented to 801, begun by the Frankish king Louis the Pious, and consecrated in the 10th century. In the days of Ramón Berenguer the elder (11th Century), this parish church was used as a cathedral while the Romanesque cathedral was being built. The Gothic building phase dates from 1342-1574. Relics belonging to both saints are kept in a small chest from the cathedral of Narbonne donated by Jaume I's wife.