Australia is the world's smallest and flattest continent, located between the Indian and Pacific oceans. It has some of the oldest and least fertile soils on Earth. Indigenous Australians have lived on the continent for over 50,000 years, with a complex hunter-gatherer society. Today, Australia has a Western cultural identity and its economy is highly developed and the third freest in the world, though over one-third of the country is desert. Some of Australia's most famous natural landmarks include the Great Barrier Reef, Sydney Opera House, and Ayers Rock.