There are two parking lots near Genghis Khan's Mausoleum, according to the AutoNavi navigation app: one at the Genghis Khan Mausoleum Parking Lot and the other at the Genghis Khan Mausoleum Tourist Area Mausoleum Palace.
The Genghis Khan Mausoleum Parking Lot is relatively new and is about four or five kilometers from the palace. A 20-yuan shuttle bus is required. It's mainly a large plaza with some cavalry sculptures, but not much else to see. There used to be a Mongolian Cultural Museum, but it's closed due to dilapidated conditions.
It's recommended to navigate directly to the Genghis Khan Mausoleum Tourist Area Mausoleum Palace, where there's a parking lot and the actual mausoleum palace is located. Genghis Khan's actual mausoleum is unknown due to his secret burial. Currently, it mainly houses his utensils and the Eight White Rooms, eight small white yurts, similar to cenotaphs, where used bows and arrows are stored as memorials. The building itself is well-built, but I find the lack of information about his life, history, and exhibitions a bit disappointing.