The Yin Mountains , also known colloquially as the Daqing Mountains , and in Mongolian as Dalan Qara, Dalan Terigün, Dalan Khar, Moni Ayula, and Moni Uul, are mountains in the steppe forming the southern border of the eastern Gobi Desert of the Inner Mongolia Autonomous Region, as well as the northern part of Hebei province.