Inside the vaulted interior of this cathedral, beyond its impressive marble facade sporting two orders of columns taken from the Roman amphitheatre, lie the relics of the city's patron saint. Its other famous resident is the world-famous Catanian composer Vincenzo Bellini, his remains transferred here in 1876, 41 years after his death in France. Consider visiting the Museo Diocesano next door for access to the Roman baths directly underneath the church.
The young virgin Agata resisted the advances of the nefarious Quintian (AD 250) and was horribly mutilated (her breasts were hacked off and her body rolled in hot coals). You can actually visit the dungeons where these atrocities were committed under the Chiesa di Sant'Agata al Carcere behind the Roman amphitheatre on Piazza Stesicoro. The saint's jewel-drenched effigy is ecstatically venerated on 5 February in one of Sicily's largest festivals.