Frankopan Castle anchors the seaward corner of Kamplin Square and is the most visible reminder of the noble family that ruled Krk from the early thirteenth century until 1480. The square tower at the front is the oldest part, with the round bastion added later. The walls extend along the harbour and incorporate the medieval town gates.
The castle is open to climb in season — the views from the top take in the harbour, the cathedral, and the channel between Krk and the mainland. Inside the walls there's not a huge amount to see, but the structure itself, with its mixture of Frankopan and Venetian masonry, is the point.
Kamplin Square outside doubles as the town's social heart, with cafes spilling onto the cobbles and summer concerts staged against the castle wall.