"Danube River - the second longest in Europe after the Volga. It rises in the Black Forest mountains of western Germany and flows for some 1,770 miles (2,850 km) to its mouth on the Black Sea. Along with its course, it passes through 10 countries: Germany, Austria, Slovakia, Hungary, Croatia, Serbia, Bulgaria, Romania, Moldova, and Ukraine."
"Golubac was a medieval fortified town on the south side of the Danube River, 4 km downstream from the modern-day town of Golubac, Serbia. The fortress, which was most likely built during the 14th century, is split into three compounds which were built in stages. It has ten towers, most of which started square, and several of which received many-sided reinforcements with the advent of firearms."
An image was taken near the fortress of Golubac, in the east of Serbia.