The walled centro storico is a tight grid of whitewashed alleys, painted doorways, low arches, and improbably blue glimpses of the Adriatic between buildings. The defensive walls, rebuilt in the 16th century on earlier Aragonese foundations, still ring the old town and can be followed almost all the way around.
Highlights inside the walls include the small Byzantine church of San Pietro (often closed but worth checking) with surviving 9th to 11th-century frescoes, the bishop's palace next to the cathedral, and the Porta Alfonsina, the only original gate still standing. Most of the lanes are car-free and pedestrian, lined in summer with small ceramic shops, gelaterie, and seafood places spilling tables outside.