Although Australia is the world's sixth-largest country by total land area of 7,682,300 sq km. and gives it a wide variety of landscapes, with tropical rainforests in the north-east, mountain ranges in the south-east, south-west and east, and dry desert in the centre. It is the flattest continent, with the oldest and least fertile soils; desert or semi-arid land commonly known as the outback makes up by far the largest portion of land