The Chapel of the Relics is the only chapel in the church that is constructively closed on all sides. Its interior can be viewed through the wrought iron bars that are always kept closed. Inside we can see:
- A magnificent polychrome wooden altarpiece, in pure Baroque style, with 23 relics placed in 17th century reliquaries or lanterns for their protection. 16 in torsos, 3 in the form of arms, and 4 eyes.
- A carving of the Child from the 17th century.
- An 18th-19th century cross and wrought iron bars that show remains of polychrome. A polychrome coffered ceiling with elements that form a unit in which the coffered ceiling, studded with stars, is a symbolic representation of the firmament.
- It is in the baroque style. In it were kept a multitude of relics that the Cardinal had brought on his frequent trips to Rome. They were deposited in the spaces of the images and figures that are in said chapel, inside gold and silver boxes (normal in these cases). They all disappeared during the three Napoleonic invasions that Monforte suffered and a subsequent robbery. Among them the “Lignum Crucis” (two pieces of the True Cross of the Cross, the pectoral of the Cardinal. A reliquary of the holy “thorn of the Redeemer’s crown”, made of embossed and gilded silver, was saved. It was saved from theft by to be away from this place on those dates, on the occasion of some prayers for rain.
