Australia, officially the Commonwealth of Australia, is a country comprising the mainland of the Australian continent, the island of Tasmania and numerous smaller islands. Consisting of six states and ten territories, Australia has a total area of 7,688,287 km², making it the sixth-largest country in the world and the largest country by area in Oceania. It is t…Australia, officially the Commonwealth of Australia, is a country comprising the mainland of the Australian continent, the island of Tasmania and numerous smaller islands. Consisting of six states and ten territories, Australia has a total area of 7,688,287 km², making it the sixth-largest country in the world and the largest country by area in Oceania. It is the world's oldest, flattest, and driest inhabited continent, with some of the least fertile soils. It is a megadiverse country, and its size gives it a wide variety of landscapes and climates including deserts in the interior and tropical rainforests along the coast. Its population of more than 28 million is highly urbanised and heavily concentrated on the eastern seaboard. Canberra is the nation's capital, while its most populous cities are Sydney and Melbourne, both with a population of more than 5 million.