Kotor is the most compelling city on the Montenegrin coast — a medieval Venetian town enclosed by 4.5km of walls that climb steeply up the rocky hillside behind it. The old town is a tight maze of marble-paved lanes, Romanesque churches, and small piazzas, with cats lounging on every warm surface (Kotor has taken the stray cat as its unofficial symbol and embraces it fully).
The Bay of Kotor surrounding it is often described as Europe's southernmost fjord — it isn't technically a fjord but it does have that enclosed, dramatic quality, with limestone mountains rising almost vertically from the water. Coming in by boat is the best arrival; driving in from the north involves a spectacular serpentine descent from the Lovćen massif.
The market outside the city walls sells dried figs, mushrooms, prosciutto, olive oil, and local cheese — buy something for the road. The walk up to the fortress above the town takes about 45 minutes and rewards with views over the whole bay; go early morning before the heat and crowds. The Cathedral of Saint Tryphon, the patron saint of Kotor, is the main church and worth a look inside.
Kotor is a major cruise ship destination. When ships are in port (usually mid-morning to late afternoon), the old town is extremely crowded. Come early, or plan around the ship schedules. The town is much more pleasant on evenings and mornings when the day-trippers have left.
Good base for exploring the bay: Perast is 12km away, Herceg Novi about 40km.