The sanctuary lies in between the Anamalai hills and Nelliampathy hills. Altitude ranges between 300m and 1438m above MSL. There are 7 major valleys and 3 major river systems. Geologically the sanctuary has Hornblende biotite gnesis and charnockites. Major peaks in the sanctuary are Karimala (1438m), Pandaravarai (1290m) ,Kuchimudi, Vengoli (1120m) and Puliyarapadam (1010m). Apart from the natural rivers and streams, the sanctuary possesses 3 man-made reserviors namely Parambikulam, Thunacadavu and Peruvaripallam whose cumulative waterspread is 20.66 sq. km.