Romania [ɹoʊˈmeɪniə] (dated: Rumania, Roumania; Romanian: România, IPA: [ro.mɨˈni.a]) is a country located in South-East Central Europe, North of the Balkan Peninsula, on the Lower Danube, within and outside the Carpathian arch, bordering on the Black Sea. Almost all of the Danube Delta is located within its territory. It shares a border with Hungary and Serbia to the west, Ukraine and the Republic of Moldova to the northeast, and Bulgaria to the south. Romania has the 9th largest territory and the 7th largest population (with 22 million people) among the European Union member states. Its capital and largest city is Bucharest (Romanian: Bucureşti /bu.kuˈreʃtʲ/ (help·info)), the 6th largest city in the EU with 1.9 million people. In 2007, Sibiu, a city in Transylvania, was chosen as a European Capital of Culture. Romania also joined NATO on March 29, 2004, and is also a member of the Latin Union, of the Francophonie and of OSCE. Romania is a semi-presidential unitary state. With a surface area of 238,391 square kilometres (92,043 sq mi), Romania is the largest country in southeastern Europe and the twelfth-largest in Europe. A large part of Romania's border with Serbia and Bulgaria is formed by the Danube. The Danube is joined by the Prut River, which forms the border with the Republic of Moldova. The Danube flows into the Black Sea within Romania's territory forming the Danube Delta, the second largest and the best preserved delta in Europe, and a biosphere reserve and a biodiversity World Heritage Site. Other important rivers are the Siret, running north-south through Moldavia, the Olt, running from the oriental Carpathian Mountains to Oltenia, and the Mureş, running through Transylvania from East to West.