High Quality Content by WIKIPEDIA articles! The Greater Toronto Area (GTA) is the largest metropolitan area in Canada, with a 2006 census population of 5.5 million. The Greater Toronto Area is usually defined as the central city of Toronto, along with four regional municipalities surrounding it: Durham, Halton, Peel, and York. The area is at the centre of the Golden Horseshoe urban agglomeration, which contains approximately one-fourth of the population of Canada.