Trsat Castle sits on a promontory above the Rječina gorge, about 138 metres above sea level, and the views over the Kvarner Gulf and the islands beyond are exceptional on a clear day. The castle itself is partly ruined and partly restored; it hosts art exhibitions, summer concerts, and open-air theatre in the warmer months, and admission is free.
To get there from the city centre, take the Trsat Staircase — 561 steps that climb directly from the Rječina riverbank. It is a serious climb but the steps are historic in themselves, lined with votive chapels and offering views back over the rooftops as you rise. If you prefer not to walk up, taxis and buses serve the hilltop. The Sanctuary of Our Lady of Trsat, a major pilgrimage church, is a short walk from the castle entrance.