The Herceg Novi old town is amazing. It is on a fairly steep hill that leads all the way down to the sea. Wandering through the small stairways to the various plazas and fortresses is a many hour adventure. There are both Orthodox and Catholic churches that are well worth visiting. The Kanli Kula fortress dominating the old town doubles as an open-air theatre and is worth visiting mainly for the splendid views of the town and the Kotor bay. The Spanjola fortress located higher up the mountain (170 meters above see level) dates back to 16th century. Take a small street going upwards across from the Kanli Kula fortress. Entrance is free and you can freely climb (and fall from) the walls.