Kiev is the largest city of Ukraine, located in the north central part of the country on the Dnieper River. Kiev is an important industrial, scientific, educational and cultural centre of Eastern Europe. It is home to many high-tech industries, higher education institutions and world-famous historical landmarks. The city has an extensive infrastructure and highly developed system of public transport, including the Kiev Metro. As of April 2007, official municipal estimates placed the population of Kiev at about 2.7 million inhabitants, although some much higher unofficial estimates are often published. Geographically, Kiev belongs to the Polesia ecological zone (a part of the European mixed woods). Kiev is located on both sides of the Dnieper River, which flows south through the city towards the Black Sea. Kiev has a continental humid climate. The warmest months are June, July, and August, with mean temperatures of 13.8 to 24.8 °C (56.9 to 76.7 °F). The coldest are December, January, and February, with mean temperatures of −4.6 to -1.1 °C (23.7 to 30.0 °F).