The Commonwealth of Australia is a country in the southern hemisphere comprising the mainland of the world's smallest continent, the major island of Tasmania, and a number of other islands in the Indian and Pacific Oceans. The neighbouring countries are Indonesia, East Timor, and Papua New Guinea to the north, the Solomon Islands, Vanuatu, and New Caledonia to the north-east, and New Zealand to the south-east. Australia is the only country that is also a continent. The Australian mainland has been inhabited for more than 42,000 years by indigenous Australians. After sporadic visits by fishermen from the north and then European discovery by Dutch explorers in 1606, the eastern half of Australia was later claimed by the British in 1770 and initially settled through penal transportation to...more >> the colony of New South Wales, commencing on 26 January 1788. As the population grew and new areas were explored, another five largely self-governing Crown Colonies were established during the 19th century. On 1 January 1901, the six colonies became a federation, and the Commonwealth of Australia was formed. Since federation, Australia has maintained a stable liberal democratic political system and remains a Commonwealth realm. The capital city is Canberra, located in the Australian Capital Territory (ACT). The population is just over 21.3 million, with approximately 60% of the population concentrated in and around the mainland state capitals of Sydney, Melbourne, Brisbane, Perth, and Adelaide.