by the Soviet occupation authorities and large swathes of previously residential areas were turned into parks and parking lots. After the war, the Soviet authorities declared Tartu a "closed town for foreigners", as an airbase for bombers was constructed on Raadi Airfield, in the northeast outskirts of the city. It was one of the largest military airbases in the former Eastern Bloc and housed strategic bombers carrying nuclear bombs. On one end of an older strip of the runway, the new building of Estonian National Museum was built. Tartu Airport was opened in the south of the city in 1946. Besides the airport Estonian Aviation Academy was established in 1993. Privately owned Estonian Aviation Museum, which is 5 km to the East from the airport (7 km by car), was opened to the public in 2002. During the 1944–1991 Soviet occupation the population of Tartu almost doubled from 57,000 to above 100,000 — due to mass immigration from Russia and other areas of the former Soviet Union, in large part because of the military airbase. Modern era Since Estonia regained its independence in 1991, the old town centre has been renovated. Notably, St. John's Church, in ruins since World War II, has been restored. Many new commercial and business buildings have been erected (Tartu Kaubamaja, Tasku, Emajõe kaubanduskeskus, Lõunakeskus, Kvartal, etc.). The highest residential building and local landmark Tigutorn was opened in 2008. The AHHAA science centre relocated to a new building in 2011 and the Estonian National Museum's new main building opened in 2016. Geography Climate Tartu lies within the temperate humid continental climate zone (Dfb). The climate is rather mild considering the high latitude, largely due to the proximity of the Baltic Sea and warm airflows from the Atlantic. Nevertheless, continental influence can be felt on hot summer days and cold spells in winter, when the temperature can occasionally (but rarely) drop below . Generally, summers are warm and winters are cold. The Tartu weather station is located in Tõravere village, which is about 20 kilometers from the city, so the actual temperature in the city may be slightly warmer than the official average temperatures. Economy Mostly known as a university town, Tartu is also a site of heavy industry. The food industry has traditionally been important for the town's economy and some bigger companies in the field include A. Le Coq, Tartu Mill and Salvest. Kroonpress is