Slovenia is a nation state in southern Central Europe at the crossroads of main European cultural and trade routes.] It borders Italy to the west, Austria to the north, Croatia to the south and southeast, and Hungary to the northeast. It covers 20,273 square kilometers (7,827 sq mi). It is a parliamentary republic and a member of the European Union and NATO .Its capital and largest city is Ljubljana. Four major European geographic units meet on the territory of Slovenia: the Alps, the Dinaric Alps, the Pannonian Plain, and the Mediterranean, with a small portion of coastline along the Adriatic Sea. The territory has a mosaic structure and an exceptionally high landscape and biological diversity, which are a result of natural attributes and the long-term presence of humans. The country is one of the most water-rich in Europe. Although the climate in the mainly hilly territory is influenced by the continental climate, the Slovene Littoral has the sub-Mediterranean climate, while the Alpine climate is found in the north-western part of the country.