Hilltops are in the southern region of New South Wales and sit atop a large granite rock. This big rock is 150km long and 50km wide and blocks the westward flow of the Murrumbidgee River from Australia’s national capital, Canberra. Over aeons, the rock has weathered to produce a layer of decomposed granite soil up to 15-metres deep. Dust storms from central Australia deposited red sand and clay onto this soil, especially on the leeward side of ridges. This event produced the distinctive red colour and clay layers in the soil.