Serbia, officially the Republic of Serbia, is a country located at the crossroads of Central and Southeast Europe, covering the southern part of the Pannonian Plain and the central Balkans. Serbia is landlocked and borders Hungary to the north; Romania and Bulgaria to the east; Macedonia to the south; and Croatia, Bosnia, and Montenegro to the west; it also borders Albania through the disputed territory of Kosovo. The capital of Serbia, Belgrade, is among Europe's oldest cities and one of the largest in Southeast Europe.Serbs established several states in the early Middle Ages following the Slavic migrations. The Serbian Kingdom obtained recognition by Rome and Constantinople in 1217; the state was elevated to the Serbian Empire, in 1346. By the mid-16th century, the entire territory of modern-day Serbia was annexed by the Ottoman Empire, at times interrupted by the Habsburgs. In the early 19th century, the Serbian revolution established the nation-state as the region's first constitutional monarchy, which subsequently expanded its territory and pioneered the abolition of feudalism in the Balkans. Following disastrous casualties in World War I, and subsequent unification of Habsburg crownlands of Vojvodina and Syrmia with Serbia, the country co-founded Yugoslavia with other South Slavic peoples, which would exist in various formations until 2006, when Montenegro declared its independence. In 2008 the parliament of UNMIK Kosovo declared independence, with divergent responses from the international community.Serbia is a member of the UN, CoE, OSCE, PfP, BSEC, and CEFTA. It is also an official candidate for membership in the European Union, which is negotiating its EU accession, acceding country to the WTO and is a militarily neutral state.Serbia has a high HDI and provides a universal health care system and free primary and secondary education. Among the region's highest-scored "free countries" Serbia is an upper-middle income economy with the service sector dominating the country's economy, followed by the industrial sector and agriculture.