a vast, flat plain that extends across central australia____________.

This may be what you need:

http://en.wikipedia.org/wiki/Outback

Yes, the vast, flat plain that extends across central Australia is commonly referred to as the "Outback." The Outback is a remote and sparsely populated region, characterized by arid and semi-arid landscapes, including deserts, grasslands, and scrublands. The term "Outback" is often used to describe the vast expanse of land that is located far away from major cities and urban centers. To learn more about the Outback and its various features, you can refer to the link provided, which will give you a detailed explanation of this unique and fascinating region.