Poland, officially the Republic of Poland, is a country in Central Europe. It extends from the Baltic Sea in the north to the Sudetes and Carpathian Mountains in the south, and has a temperate transitional climate, while its longest river is the Vistula. Poland is the fifth-most populous member state of the European Union, with its sixteen voivodeships comprising a total population of over 38 million and covering a combined area of 312,696 km2 (120,733 sq mi).