Oslo is Norway's capital and largest city, with 700,000 citizens in the city proper and about 1.5 million inhabitants in greater Oslo. It is in the East of the country in the Oslofjorden fjord, extending over an inlet of the Skagerrak strait. It is spaciously laid out and surrounded by green hills and mountains and includes 40 islands and 343 lakes. Oslo offers ski slopes for alpine skiing and ski trails for cross-country skiing in the winter. In the summer, the temperature in Oslo may make it comfortable to swim. There are several well-visited beach resorts. Oslo is one of the world's northernmost capitals and so gets only 6 hours of sunlight in the winter. In high summer, sunlight hours soar to 18, making its climate markedly different between seasons, with cold yet relatively dry winters.
A relatively compact city squeezed into a thin strip of land along the shoreline, Oslo prides itself as one of the world's most sustainable cities. Central parts of the city are compact, but Oslo as a whole is relatively spacious. While it holds an array of historic monuments, Oslo is perhaps most famous for its modern architecture, including striking and daring projects launched at the turn of the millennium. Oslo's economy is powered by the maritime industry, high-tech and clean energy sectors. In 2010, Oslo was ranked as the world's most expensive city to live in by the Swiss wealth management company UBS AG.
Oslo is Norway's economic and demographic centre, as well as the hub for most domestic and international transport. Despite Oslo's population density there is never more than 300 meters' walk to a park or green area from any residence in the city.