Mongolia has no dearth of open land … 🙂 When you travel to Ulaanbaatar from Beijing, you cross the Gobi desert. One can note a lot of wild camels, horses Etc. The Gorkhi-Terelj National Park is around 40 Km from Ulaanbaatar by road. During my 3-4 hours in the park, I was very impressed with the amazing scenery.
I suggest that you rent a car (with driver, which is what I did) from your hotel. That way you can explore the park, which is huge, at your own pace and spent time at points which are of interest to you. On the way, you can also visit the huge Genghis Khan Statue Complex.