The Greater Toronto Area (GTA) is the most populous metropolitan area in Canada. At the 2011 census, it had a population of 6,054,191, and the census metropolitan area had a population of 5,583,064. The Greater Toronto Area is defined as the central city of Toronto, and the four regional municipalities that surround it: Durham, Halton, Peel, and York. The regional span of the Greater Toronto Area is sometimes combined with the city of Hamilton, Ontario and its surrounding region, to form the Greater Toronto and Hamilton Area. The Greater Toronto Area is the northern part of the Golden Horseshoe.