Toronto is the largest city in Canada, and the provincial capital of Ontario, it is located on the northwestern shore of Lake Ontario. With over 2.5 million residents, Toronto is at the heart of the Greater Toronto Area (GTA), and is part of a densely-populated region in south-central Ontario known as the Golden Horseshoe.The census metropolitan area (CMA) had a population of 5,113,149, Toronto's leading economic sectors include finance, business services, telecommunications, aerospace, transportation, media, arts, film, television production, publishing, software production, medical research, education, tourism and sports industries. The Toronto Stock Exchange, the world's fifth largest, is headquartered in the city, along with a majority of Canada's corporations. which reflects its role as an important destination for immigrants to Canada. United Nations Educational, Scientific and Cultural Organization (UNESCO) also rated Toronto as the world's most diverse city, as about 49 percent of the population were born outside of Canada. Because of its low crime rates, clean environment and generally high standard of living, Toronto is consistently rated as one of the world's most livable cities by the Economist Intelligence Unit and the Mercer Quality of Living Survey. In addition, Toronto was ranked as the most expensive Canadian city in which to live in 2006.
Residents of Toronto are called Torontonians. Toronto has a number of sister cities, which are selected based on economic, cultural and political criteria."