Hungary, officially the Republic of Hungary, is a landlocked country in the Carpathian Basin in Central Europe, bordered by Austria, Slovakia, Ukraine, Romania, Serbia, Croatia, and Slovenia. Its capital is Budapest. Hungary is a member of EU, NATO, OECD, V4 and is a Schengen state. The official and vernacular language is Hungarian, which is part of the Finno-Ugric family, thus one of the four official languages of the European Union that are not of Indo-European origin. A great power until the end of World War I, Hungary lost over 70% of its territory, along with one third of its population of Hungarian ethnicity, under the Treaty of Trianon. The kingdom was succeeded by a Communist era (1947–1989) during which Hungary gained widespread international attention regarding the Revolution of 1956 and the seminal move of opening its border with Austria in 1989, thus accelerating the collapse of the Eastern Bloc. The present form of government is a parliamentary republic. Today, Hungary is a high-income economy, and a regional leader regarding certain markers. Until recently, it was listed as one of the 15 most popular tourist destinations in the world. The country 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.