Australia is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. It is the largest country in Oceania and the world's sixth-largest country by total area. The population of 26 million is highly urbanized and heavily concentrated on the eastern seaboard. Australia's capital is Canberra, though its largest city is Sydney. The country's other major metropolitan areas are Melbourne, Brisbane, Perth, and Adelaide. Australia is the oldest, flattest, and driest inhabited continent, with the least fertile soils. It has a landmass of 7,617,930 square kilometers (2,941,300 sq. mi). A megadiverse country, its size gives it a wide variety of landscapes, with deserts in the center, tropical rainforests in the north-east, and mountain ranges in the south-east. Australia generates its income from various sources including mining-related exports, telecommunications, banking, manufacturing, and international education