Don River – Wikipedia

The Don rises in the town of Novomoskovsk 60 kilometres (37 mi) southeast of Tula (120 km south of Moscow), and flows for a distance of about 1,870 kilometres to the Sea of Azov. From its source, the river first flows southeast to Voronezh, then southwest to its mouth. The main city on the river is Rostov on Don.

https://en.wikipedia.org/wiki/Don_River_%28Russia%29