FOR THOSE WHO ONLY HAVE FEW DAYS. 

This circuit of just under 500 km is suitable for those who don't have much time and want to get out of the city as quickly as possible.
At 50 km, you can visit the Manzuchir Monastery, not far from the town of Zunmod. You then head due south into the Gobi Desert to reach the sacred mountain of Zorgol Khairkhan. This site is venerated and revered by the locals, who believe it is the seat of a great, benevolent spirit. The huge, red granite mountain does indeed have a diverse and beautiful nature to offer. It has many caves and water springs, home to the Argali wild sheep, ibexes, red deer, and many other animals. There is a tourist camp where you can sleep, otherwise it's wild camping. The next day, head to the Tuul River. There is a small village at the beginning of the day where you can stock up on water, fuel, and food. A little beyond the village of Undursheeret, you'll find a small, pleasant family-run tourist camp to spend the night: https://maps.app.goo.gl/dBWaiXMsXULVX4nM7 or a small hotel at the entrance to the village of Lun: https://maps.app.goo.gl/pzpTk6m2TUvs8o8U7
Then it's back to UB via Hustai National Park. For those who aren't in a hurry to get back, there's always the option of spending the night in a tourist camp in Molstog.