Rhodope Mountains Pyrenees Mountains Balkan Mountains Caucasus Mountains
Struma River Danube River Iskar River Maritsa River
Serbia Macedonia Greece Turkey Greece Macedonia Romania Russian Federation
Baltic Sea Caspian Sea Mediterranean Sea Black Sea
Plovdiv Sofia Rousse Burgus
Russian Ottoman Mongol British
Backhoro Monastery Aladzha Monastery Rila Monastery Troyan Monastery
8 million 180 million 1.8 million 80 million
Romania Turkey Serbia Greece