The great temple, which is circular in shape, is formed by two large, sacred halls, the upper church and the crypt. The parts of the building are not designed separately, but rather as parts of a single architectural entity. 
The inside of the Grande Chiesa church offers bright light, thanks to the space being proportionally divided by the large cylindrical walls, which open up towards the altar. The light comes from a huge concave glass window, on the façade, and from a cross-shaped skylight which unfolds along the roof, converging into a gap that symmetrically divides the apse. Chapels were placed on the sides so that visitors could cultivate their mercy privately. The church features many confessionals, both in the temple and in the crypt. The main altars are made from Pentelic marble, while the floors are Prodo marble.