The interior has a Latin cross plan, with a nave and two aisles divided by pilasters. In the first two chapels of the right aisle are the tomb of emperors and royal figures moved here in the 18th century from their original sites (mostly from the basilica itself). Here are the remains of Emperor Henry VI, his son Frederick II, as well as those of Peter II of Sicily. A Roman sarcophagus is the tomb of Constance of Aragon, Frederick's wife. Under the mosaic baldachins are the tombs of Roger II, the first King of Sicily, and his daughter Constance. The last two were once located in the transept of the Cathedral of Cefalù.