The Murray Darling Depression , also known as the Murray-Darling woodlands and mallee, is a 19,717,651 HA biogeographic region and an ecoregion in southeastern Australia consisting of a wooded plain through which flow two of Australia's biggest rivers, the Murray and the Darling. There are several modern human settlements in the bioregion including Ivanhoe and Manilla, but the region also contains some of the oldest known human occupation sites in Australia.