The Kanli Kula crowns the old town and is the obvious first stop. The Ottomans built it in the 16th century on the highest point inside the city walls; the Venetians and Austrians later reinforced it. Inside, the upper terraces have been converted into a 1,000-seat open-air theatre, but most of the original masonry is intact: thick ramparts, vaulted chambers, narrow firing slits.
Pay the small entrance fee at the gate and climb to the top. From the upper wall the whole entrance to the Bay of Kotor opens up — Prevlaka peninsula in Croatia to the west, the Luštica peninsula across the strait, the open Adriatic beyond. It's the best view in town and worth timing for late afternoon.