The Nišava or Nishava (Bulgarian and , ) is a river in Bulgaria and Serbia, a right tributary, and with a length of also the longest one, of the South Morava. Course Bulgaria The Nišava originates in western Bulgaria, in the Stara Planina mountains (east of Kom Peak) near the village of Gintsi. Its source is close to the Serbian border. It enters Serbia after of flow through Bulgaria without receiving any major tributaries. Because it flows through Gintsi, the upper course of the river is known as Ginska (Cyrillic: Гинска). It first flows to the south, then sharply turns west into the Godech Kettle, passing through Razboishte, after which it forms a gorge. Coming out of the gorge, it reaches Kalotina, a major border crossing on the Bulgarian-Serbian border (Kalotina-Gradina), and continues to the west into Serbia. Serbia Flowing generally to the west for the remaining , it passes near Dimitrovgrad, Pirot, Bela Palanka, Niška Banja and Niš, one of the largest cities in Serbia, after which the Nišava empties into the Južna Morava. However, with the rapid growth of Niš in previous decades and its still fast growing suburbs, the banks of the Nišava are urbanized almost to its mouth. Geography The river belongs to the Black Sea drainage basin. Its own drainage area covers , of which about 73% in Serbia, the rest in Bulgaria. The Nišava is not navigable. It is not only the longest tributary of the Južna Morava, but also the largest one in terms of discharge (). It has many smaller tributaries, the most important being the Temštica from the right, and the Jerma (or Sukovska reka), Crvena reka, Koritnička reka and Kutinska reka from the left. In its Serbian part, the Nišava carved a composite valley with several depressions (Dimitrovgrad, Pirot (or Basara; Cyrillic: Басара), Bela Palanka and Niš). However, the most prominent geological feature the river formed is the Sićevo gorge. There are numerous caves in the step-like limestone cliffs, majority of which remains unexplored. Sićevo gorge The gorge is located between Bela Palanka and Niška Banja. The gorge is long, and deep. The gorge is a composite one, which means in consists of several gorges and widenings, like the Prosečka gorge, Ostrovička basin or Gradištanski canyon. The river is quite powerful in the gorge, which is used for two power stations ("Sićevo" and "Ostrovica") used for electricity production, irrigation and