The old town of Ribnik from the 13th century is the only preserved lowland fortress in Croatia, the so-called wasserburg because it was once surrounded by a pond for defensive purposes. It is located in the swampy plain where the Obrh stream flows. Its first owners were the princes of Gorizia Babunići, and from the 14th century. the owners were the Frankopans of Krk whose coat of arms is still above the main entrance.
It is not open to visitors except during events (eg Chestnut Festival Via Ribnik in October)