Well, Belgrade is not nearly that old as Yerevan, although in its broader area were some of the oldest settlements in Europe, more than 7000 years old. However

Well, Belgrade is not nearly that old as Yerevan, although in its broader area were some of the oldest settlements in Europe, more than 7000 years old. However todays Belgrade fortress (called Kalemegdan) sits on the very same place where Celts built their fortification around 300 BC. In 2nd century BC Romans turned it into their city called Singidunum. Most of the today's fortress walls are from the medieval and later times, but some parts of the Roman walls are still visible today, and the big Roman well that was used to supply the city with water still exists and it's open to tourists. Unfortunately most of the roman structures outside the fortress are nowadays under the modern city of Belgrade, but the position and the layout of the fortress didn't change much. Danube and Sava rivers still run under it and the hill looks the same, so I presume that some ancient tourists wouldn't have hard time to recognize it immediately.