The Hangai Mountains cause precipitation, and the runoff to the south empties into the Gobi, eventually creating the Gobi lakes of Böön Tsagaan Nuur and Orog Nuur. These are prime birding locations for the Gobi relict gull etc.
How to travel there:
There are flights three times a week to Bayanhongor. Overland drive is far, but possible. We visit this area on our bird watching trips.