The Brod na Kupi–Tršće section of the Cycling Trail of Gorski Kotar takes you upstream, along the upper flow of the Kupa river, whose preserved environment and biodiversity makes for a perfect home to more than 100 diurnal butterfly species. The entire Kupa river valley is often nicknamed the “Butterfly Valley” for this very reason. The road will take you along the right bank of the Kupa river, through the picturesque hamlets of Kuželj, Gašparci and Turke, and the numerous rapids and beaches are perfect for taking a dip. The water-powered mill and sawmill in Zamost and the ethnological collection of the house of Palčava Šiša in Plešce are also a must-visit. The development of this area is credited to Petar Zrinski, who had an iron smelting plant built in Čabar in 1651. The most famous structure in Čabar is the 16th-century Zrinski Castle, located only 700 metres from the Čabranka river source. A more demanding ascent awaits you on the way from Čabar to Tršće, but every metre crossed will be well worth the effort.