Oslo is the capital of Norway, a modern city with numerous parks and recreational areas. While European cities are known for their leadership in sustainability and green lifestyle, Oslo is one of the cities that tries to be on top of things when it comes to the environment. Oslo produces the least CO2 emissions of all European cities and was one of the first to give up oil heating in buildings in favour of renewable energy. The city’s public transportation system is very developed and a bike rental system makes it very accessible. Oslo received The European Sustainable City Award in 2003 and in 2007 Reader's Digest ranked Oslo as number two on a list of the world's greenest, most livable cities.