Khar Balgas, also known as Ordu-Baliq, is the ruined capital of the Uyghur Khaganate on the Orkhon Valley steppe, north of Karakorum. The remains are low, weathered, and spread across open grassland, but the scale matters: this was a major city before the Mongol capital rose nearby.
You need imagination here, and preferably a guide who can point out walls, gates, and citadel traces that might otherwise blur into the steppe. For travellers interested in Mongolia before Chinggis Khan, it adds useful depth to the Karakorum and Orkhon Valley story.