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