Serbia is a country on southeast Europe's Balkan peninsula with northern plateaus and mountains with ski resorts to the south. Capital city Belgrade is home to Communist-era architecture and Kalemegdan Park, site of Belgrade Fortress, held successively by the Roman, Byzantine and Ottoman empires. Stari Grad, the old city, is home to 19th-century mansions, plus opera and ballet at Narodno Pozori?te (national theater).