A mountain river rising below Světlá hora near Vimperk in Šumava. Its upper stream is sometimes called Třeštilka (harum-scarum) due to the sudden and dangerous rises of water during torrential rains. In Strakonice, it flows into the Otava River after 46 km. In the past, it was a part of the defence system of Strakonice Castle (together with the Blatský Pond and the Otava River) and it was often used by fullers and hosiery makers, the predecessors of tarbush producers.