The Sanctuary is an oval-shaped church meant to be a reliquary, that is, a shrine in which sacred relics are kept.
The area is harmoniously arranged with twelve pyramids, three altarpieces and eight carved panels.
The main altarpiece, located behind the altar, was built to keep the most important relics. Wooden bust-reliquaries, representing Holy Bishops, Popes, Apostles and other martyrs are arranged in graceful corbels.
Some small urns also have relics, and one of them holds the skull of a Holy Martyr named Antonio, but without any connection to the famous St. Anthony.
Other elements stand out in the altarpieces to the sides, such as an urn containing the relics of St. Comba and another, the Martyrs of Morocco.
Four Popes and four Bishops are represented through bust-reliquaries in each of the respective panels.
There are twelve high pyramids all around the Sanctuary. Each pyramid has eighteen reliquaries, while the supporting pyramids contain three reliquaries.
The lighting of the Chapel is primarily made up by the natural light that goes through the big windows around it.