country are Sofia (1,246,791), Plovdiv (376,918), Varna (345,522), Burgas (259,985), Rousse (177,538), Stara Zagora (163,193), Pleven (121,700), Dobrich (115,861), Sliven (100,300). Bulgaria has a scientific base on Livingston Island in the South Shetland Islands , Antarctica .      See also:     List of cities in Bulgaria     Rivers of