Australia, officially the Commonwealth of Australia, is a country that includes the mainland of the Australian continent, Tasmania, and numerous smaller islands. Covering 7,688,287 square kilometers (2,968,464 square miles), it is the sixth-largest country in the world and the largest in Oceania. Known as the flattest and driest inhabited continent, Australia features diverse landscapes and climates, from deserts to tropical rainforests. Aboriginal Australians, who arrived from Southeast Asia 50,000 to 65,000 years ago, spoke over 250 languages and represent one of the world’s oldest living cultures. European exploration began in the 17th century, and British colonization started in 1788 with the establishment of the penal colony in New South Wales. By the mid-19th century, several self-governing British colonies were established. These colonies federated in 1901 to form the Commonwealth of Australia, marking a shift toward autonomy from the UK. Australia is a constitutional monarchy with a parliamentary democracy, consisting of six states and ten territories. Its population of nearly 28 million is urbanized primarily, concentrated along the eastern seaboard, with Canberra as the capital and Sydney and Melbourne as the most significant cities. The country has a diverse culture, high per capita income, and ranks well in quality of life, health, and education. As a middle power, Australia has significant military expenditure. It is a member of several international organizations, including the United Nations and the Commonwealth of Nations, as well as defense alliances like ANZUS and AUKUS.