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.