Silent Valley National Park located 40 kms from Mannarkkad in the Palakkad district, echoes with the sounds of teeming wildlife. The core of the Nilgiri Biosphere Reserve is the Silent Valley National Park. Despite its name, the Silent Valley (the clamour of Cicadas is conspicuously absent here) echoes with the sounds of teeming wildlife. The Silent Valley National Park has an area of 90 sq km is located in the north eastern corner of the district. It rises abruptly to the Nilgiri Plateau in the north and overlooks the plains of Mannarkkad in the south.

Perhaps, nowhere else can one also find such a representative collection of peninsular mammals, over a 100 species of butterflies and 400 species of moths and other fauna like the Ceylon Frog Moth, Great Indian Hornbill, the Nilgiri Laughing Thrush and the Lion-tailed Macaque. The denizens of this sprawling habitat of endangered virgin tropical forests include Rare Birds, Deer and Tiger. Perhaps, nowhere else can one also find such a representative collection of peninsular mammals as in this park, which was declared a national park in 1980.

          The river Kunthi descends from the Nilgiri hills, an altitude of 2000 m above sea level, and traverses the entire length of the valley and rushes down to the plains through the deep forest. The river Kunthi never turns brown and is always crystal clear, perennial and wild.

The evapo-transpiration from these forests is much higher than from any other surfaces. This cools the atmosphere, helps easy condensation of water vapour and thus causes the summer rains.