Australia, officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the world's smallest continent and a number of islands in the Southern, Indian, and Pacific Oceans. Neighbouring countries include Indonesia, East Timor and Papua New Guinea to the north, the Solomon Islands, Vanuatu and the French dependency of New Caledonia to the northeast, and New Zealand to the southeast. The mainland of Australia has been inhabited for more than 42,000 years by Indigenous Australians. After sporadic visits by fishermen from the north and by European explorers and merchants starting in the seventeenth century, the eastern half of the mainland was claimed by the British in 1770 and officially settled through penal transportation as the colony of New South Wales on 26 January 1788. As the population grew and new areas were explored, another five largely self-governing Crown Colonies were successively established over the course of 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. The current national population is around 20.6 million people, and is concentrated mainly in the large coastal cities of Sydney, Melbourne, Brisbane, Perth, and Adelaide.