Silent Valley National Park is a national park in Kerala, India. It is located in the Nilgiri hills, has a core area of 89.52 km², which is surrounded by a buffer zone of 148 km². This national park has some rare species of flora and fauna. This area was explored in 1847 by the botanist Robert Wight. Silent Valley is home to the largest population of lion-tailed macaques, an endangered species of primate. Public controversy over their habitat led to the establishment of Silent Valley National Park.