The High Range Plateau is located around Munnar and Devikulam. It has an average elevation of about and drains to the south through Muthirapuzha into Periyar. The high Rajamala-Anamudi-Umayamala part of the main Anamalai ridge forms its northern boundary. A spur ridge starting from the main Anamalai ridge, going south immediately to the west of Munnar and continuing on to Parvathi Mala forms the western boundary of the High Range Plateau. This ridge separates the High Ranges from the Lower Periyar Valleys further to the west. The eastern edge of the High Range plateau runs north from Kolukkumala, at the junction of the High Range Plateau with the Cardamom Hills, and continues onto the Top Station along the border between Kerala and Tamil Nadu. The High Range portion is essentially the south and west draining slopes of the main Anamalai ridge with the Cardamom Hills located to its south. All the northern slopes of the main Anamalai ridge falling within Kerala drain into Idamalayar and Pooyamkutty Ar, both tributaries of Periyar.