大兴安岭
Tongliao's topography primarily consists of plains, though the northern stretch of the prefecture extends into the eastern foothills of the southern Greater Khingan. The central and eastern parts of the prefecture are marked by the plains of the Xiliao, Xinkai River (), and Jiaolai rivers (), collectively forming the Sanhe Plain (). The highest point in the prefecture is Tunte'er Peak (), at .