Adelaide is the capital of South Australia and is located on the Adelaide Plains, with a population of over 1.3 million people. EMU is a flightless bird native to Australia and is the second-largest living bird by height. Perth is the capital of Western Australia and is located on the Swan Coastal Plain, with a population of over 2 million people. Sydney is the most populous city in Australia and is located on the east coast of the continent, with a population of over 5 million people. OPAL is a precious gemstone found in Australia and is the national gemstone of the country.