The interior is refined and stunning, a great masterpiece of decoration. In the lunette opposite the entrance and above one of the three sarcophagi in the mausoleum, St. Lawrence, to whom the building is dedicated, shoulders the Cross and holds the open Book of the Laws. Apostles are in the larger lunette.
Mosaics decorate the building from midway up the wall and across the entire ceiling.
Everything feels as if it were shimmering in the sky.