Boka stream collects water in the Kanin mountain range. It flows through the underground caves and comes out on a 30 m rocky ledge. After that the Boka stream falls over a 106 m high cliff (Boka waterfall). Together withe the shallower bottom part, Boka waterfall measures 136 m which makes it the highest waterfall in Slovenia. In the driest periods it has a flow of two cubic meters per second, the abundant rainfall increases circulation to the majestic hundred cubic meters per second. The length of the stream to the mouth of the Soca is less than one kilometer, making it one of the shortest rivers in Slovenia.