Romania is a unitary semi-presidential republic located in southeastern Europe north of the Balkan Peninsula. It borders Hungary, Serbia, Ukraine, Moldova, and Bulgaria, with a population of over 20 million. Romania emerged from territories of the former Roman Empire and gained independence from the Ottoman Empire in 1877. After World War II it became a socialist republic within the Soviet sphere of influence but transitioned to a democratic government and market economy following the fall of communism in 1989. Tourism is an important industry for Romania's economy, attracting over 3.5 million visitors annually to attractions like the Black Sea coast, medieval towns, and castles. Historically, Romanian scientists and inventors have made contributions in many fields including aviation