The Cathedral of San Cataldo is the oldest church in the city and one of the most historically complex religious buildings in southern Italy. Its origins go back to the 10th or 11th century, and successive layers of construction are still visible: a Romanesque nave, Byzantine-influenced mosaics, Norman arches, and a baroque facade added in the 18th century. The overall effect is of accumulated history rather than coherent design, which is more interesting than it sounds.
The crypt is the most atmospheric part of the building — a low, forest of columns, most of them spoliated from ancient Greek and Roman buildings, supporting the floor of the nave above. Some have mismatched capitals; the variety of orders visible in a single underground space tells you something about how much ancient material was lying around to be reused. The Cappella di San Cataldo, reached from the north aisle, is a startling contrast: full baroque excess in polychrome marble.