Australia, officially the Commonwealth of Australia, is a country comprising the mainland of the Australian continent, the island of Tasmania and numerous smaller islands. Australia has a total area of 7,688,287 km2 (2,968,464 sq mi), 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.