The Nisava originates in western Bulgaria, in the Balkan mountains (east of Kom Peak) near the village of Gintsi. Its source is close to the Serbian border. It enters Serbia after 67 km of flow through Bulgaria without receiving any major tributaries.
Because it flows through Gintsi, the upper course of the river is known as Ginska. 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.
Flowing generally to the west for the remaining 151 km, it passes near Dimitrovgrad, Pirot, Bela Palanka, Niska Banja and Nis, one of the largest cities in Serbia, 10 km after which the Nisava empties into the South Morava.
The Nisava valley is part of a major natural route that from ancient times has connected Europe and Asia: the route follows the valleys of the Morava, Nisava and Maritsa and onwards towards Constantinople, present-day Istanbul. Both the Belgrade-Sofia-Istanbul road and the railway follow this route.
