The Door of Forgiveness gets its name because pilgrims traveling the Camino de Santiago would enter through it, seeking to obtain the corresponding indulgences and forgiveness for their sins in this church. It opens onto the south facade of the transept and is a fine example of High Romanesque architecture; its reliefs are attributed to Master Esteban, a sculptor who also worked on the cathedrals of Pamplona and Santiago de Compostela. It was constructed after the Gate of the Lamb and marks the first time Esteban sculpted a series of Gospel themes that would later be reproduced on other portals along the Camino, such as those of the Cathedral of Compostela, Santa María in Pamplona, and Toulouse.

The façade is divided into two sections by a chequered cornice. The upper section features three large semicircular arches, with the side ones being blind, while the central columns are twin columns with Attic bases featuring claws; the central window, closed off by a Romanesque grille, completes this section. The lower section houses the portal proper, in which the tympanum is divided into three keystones with reliefs depicting scenes far removed from Mozarabic influence, although this reminiscence is preserved in the spandrels—not in the subject matter but in the arrangement of the sculptures of Saint Peter and Saint Paul, placing Saint Paul in the prominent position on the right, following the Hispanic tradition of the time.

The three scenes depicted are the Ascension, the Descent from the Cross, and the Empty Tomb, contemplated by the three Marys. The archivolts, with a beaded molding and highly curved, rest on fluted columns and are framed by a chequered molding, while the lintel rests on lion and dog heads. The Ascension, on the left, stands out for depicting Christ as if being helped or pushed toward heaven by two angels, with the halo accompanied by the inscription “Ascendo ad patrem meum et patrem vestrum.” In the center, the Descent from the Cross displays great realism, with two incense-bearing angels on the horizontal arm of the cross. On the right, the three Marys stand before the empty tomb, protected by a large-winged angel who covers the entire scene beneath a curved Romanesque arch.

These compositions by Master Esteban spread widely among the sculptors who traveled the Camino de Santiago, later extending to France and establishing an iconographic repertoire that had a notable influence on 11th-century Romanesque sculpture.