The Silent Valley National Park spreads across 89 sq. km in Kerala&rsquos Palakkad district. The park, which harbours some of the best evergreen forests in the Nilgiri Biosphere Reserve, is the catchment area of the Kunthi river. The Silent Valley came into the limelight in the 1970s, when the government planned to dam the river. The protests that followed were the beginning of the environmental movement in India. And the entire valley was declared a national park in 1985.