South Australia is a state in the southern central part of Australia. It covers some of the most arid parts of the country. With a total land area of 984,321 square kilometres, it is the fourth-largest of Australia's states and territories by area, and second smallest state by population. It has a total of 1.8 million people, and its population is the second most highly centralised in Australia, after Western Australia, with more than 77 percent of South Australians living in the capital, Adelaide, or its environs. Other population centres in the state are relatively small; Mount Gambier, the second-largest centre, has a population of 28,684. South Australia shares borders with all of the other mainland states, as well as the Northern Territory; it is bordered to the west by Western Australia, to the north by the Northern Territory, to the north-east by Queensland, to the east by New South Wales, to the south-east by Victoria, and to the south by the Great Australian Bight.