The Old Castle (Stari Grad) is the smaller and older of Kraljevica's two Frankopan fortresses, built in the 16th century on a rocky rise above the harbour. The Frankopan dynasty controlled much of the Kvarner coast in the late medieval and early modern period, and built or improved fortresses up and down the shore. Parts of the Old Castle are ruined, but enough remains to walk around the walls and take in the views over the bay and across to Krk.
The castle is freely accessible. A short walk from the harbour through the old town brings you up to the entrance. Combine with the newer Zrinski Castle for a single morning visit.