Australia was originally inhabited by indigenous Australians. In 1770, Captain Cook discovered the coast and paved the way for Britain to establish a penal colony in New South Wales. In 1901, separate colonies formed the Commonwealth of Australia. The main cities are located along the coast, including Sydney, Melbourne, Brisbane, and Perth. Sydney has the largest and oldest city with a spectacular harbor and famous Opera House. The capital city of Canberra contains national monuments and museums and is built around large lakes. Major natural landmarks include the Great Barrier Reef, the largest coral formation in the world along the Pacific coast, and Ayers Rock in Uluru, a massive red rock formation in the Northern Territory considered very important to indigenous Australians.