Hungary /ˈhʌŋɡəri/ is a landlocked country in Central Europe. It is situated in the Carpathian Basin and is bordered by Slovakia to the north, Ukraine and Romania to the east, Serbia and Croatia to the south, Slovenia to the southwest and Austria to the west. The country's capital and largest city is Budapest. Hungary is a member of the European Union, NATO, the OECD, the Visegrád Group, and the Schengen Area. The official language is Hungarian, which is the most widely spoken non-Indo-European language in Europe.Following centuries of successive habitation by Celts, Romans, Huns, Slavs, Gepids, and Avars, the foundation of Hungary was laid in the late 9th century by the Hungarian grand prince Árpád in the Honfoglalás. His great-grandson Stephen I ascended to the throne in 1000 AD, converting the country to a Christian kingdom. By the 12th century, Hungary became a middle power within the Western world. Following the Battle of Mohács in 1526, Medieval Hungary collapsed and succumbed to 150 years of partial Ottoman occupation. Hungary eventually came under Habsburg rule, and later formed a significant part of the Austro–Hungarian Empire.Hungary's current borders were first established by the Treaty of Trianon after World War I, when the country lost 71% of its territory, 58% of its population, and 32% of ethnic Hungarians. Following the interwar period, Hungary joined the Axis Powers in World War II, suffering significant damage and casualties. Hungary came under the influence of the Soviet Union, which contributed to the establishment of a four-decade long communist dictatorship. The country gained widespread international attention regarding the Revolution of 1956 and the seminal opening of its previously-restricted border with Austria in 1989, which accelerated the collapse of the Eastern Bloc.On 23 October 1989, Hungary again became a democratic parliamentary republic, and is recognized today as a developed country. Hungary is a popular tourist destination attracting 10.2 million tourists a year. It is home to the largest thermal water cave system and the second largest thermal lake in the world, the largest lake in Central Europe, and the largest natural grasslands in Europe.