The most significant confluents are the Sušica, Lužac, Zala, Zahumčica, Golubinka, Ričinica, and Borovšćica, but they are dry for most of the year.

The best-known sight is the Gaspar Mill (Gašparov mlin) in Martinovo Selo, which was restored in the 1990s.

The first time this happened was from the 13th to 16th centuries, when it formed the border between the Lands of the Crown of Saint Stephen and the Habsburgs.

A similar thing happened in 1868, when the Rječina became the border between the Croatian and Hungarian parts of Austria-Hungary.

After World War I it became for a very short time the border between the Free State of Fiume and the Kingdom of the Serbs, Croats and Slovenes.