The Nišava river runs through the heart of Niš, and the promenade along its banks — particularly the stretch between the fortress and the city centre — is where the city does its daily walking, cycling, and socialising. In the evenings the riverfront cafes and bars fill up, strung with lights reflecting in the slow green water. On summer weekends it has real energy.
The promenade is most pleasant between the fortress walls to the west and the pedestrian King Milan Square to the east. Along this stretch you'll find outdoor cafes, ice cream vendors, benches, and a general sense of a city that knows how to enjoy a good evening. The bridge near the fortress gives a good view of both the fortified walls above and the town spreading away on either side.
The area around the confluence of the Nišava and the smaller Koritnik river, at Tvrđava (the fortress), is the most photogenic. Come in the late afternoon when the light is good and the kafanas are just filling up.