This river is called Danube. Its a northern border to Bulgaria and for Romania the south bound.
The Danube River forms part of the boundary between Bulgaria and Romania.
Romania and Bulgaria border one another and are separated by the Danube. There is no country 'in the middle'.
Iskar river (if we dont count International river Danube)
The River Danube forms the southern border of Romania. The next country to the South is Bulgaria. The River Danube is famous for the waltz of the same name.
Danube
This is the river Danube.
This is the river Danube.
The Danube river is located in Europe. It is what sets the borders for Bulgaria & Romania (which are located just north of Greece). .
The northern boundary of Bulgaria that separates it from Romania is the Danube River. The Danube River is a very important river that flows through several countries before it reaches the Mediterranean Ocean.
The norther border of Bulgaria is delineated by the Danube river. I don't know of any other river that goes "through" BG.
Follow the river Danube to Belgrade, then turn to the river Sava, which will lead you to Slovenia.