The Castle of Arta crowns a low hill at the northern edge of the old town, where the Arachthos River loops around in an almost-complete arc. The walls are largely thirteenth-century Byzantine, raised by the rulers of the Despotate of Epirus on much earlier foundations, and reworked by the Ottomans after they took the town in 1449.
The interior is mostly open ground today, dotted with the foundations of a former mosque, cisterns, and a small park, but the walls themselves are well preserved and you can walk a full circuit. The views back over the town's red roofs, the river bend, and the surrounding citrus plain are the best in Arta. Entry is free and the gates are usually open from morning till sunset.