This river drains from the Khentii Mountains, it is 819 km long and discharges into the Orkhon river. Both big and small rivers join with the Tuul river. Upstream, the river is mostly rocky, but  around Ulaanbaatar it is surrounded by a willowy forest. In the 1950s fire wood was used to create a raft, at this time the water level in the river was much higher.

River Tuul is one of three famous Mongolian rivers. It will be forever kept sacred in history, it is also mentioned in the Mongolian secret history frequently.

Since ancient times the river has been affectionately referred to as "queen Tuul" because Mongolians believe that the river Tuul is most gracious and forgiving to women.