linguistic:paraphrasing, linguistic:voice_change, structural:reformatting
Before 1639

A number of Xiongnu -era royal tombs have been discovered around Ulaanbaatar, including the tombs of Belkh Gorge near Dambadarjaalin monastery and tombs of Songinokhairkhan. Located on the banks of the Tuul River, Ulaanbaatar has been well within the sphere of Turco-Mongol nomadic empires throughout history.

Wang Khan, Toghrul of the Keraites, a Nestorian Christian monarch whom Marco Polo identified as the legendary Prester John, is said to have had his palace here (the Black Forest of the Tuul River) and forbade hunting in the holy mountain Bogd Uul. The palace is said to be where Genghis Khan stayed with Yesui Khatun before attacking the Tangut in 1226.

During the Mongol Empire (1206-1368) and Northern Yuan dynasty (1368-1635) the main, natural route from the capital region of Karakorum to the birthplace and tomb of the Khans in the Khentii mountain region (Ikh Khorig) passed through the area of Ulaanbaatar. The Tuul River naturally leads to the north-side of Bogd Khan Mountain, which stands out as a large island of forest positioned conspicuously at the south-western edge of the Khentii mountains. As the main gate and stopover point on the route to and from the holy Khentii mountains, the Bogd Khan Mountain saw large amounts of traffic going past it and was protected from early times. Even after the Northern Yuan period it served as the location of the annual and triannual Assembly of Nobles (Khan Uuliin Chuulgan).