Kolli Hills or Kolli Malai is a small mountain range located in central Tamil Nadu at a distance of 368 km from Chennai. The mountains are about 1000 to 1300 m in height and cover an area of approximately 280 km².

The mountain is a site of pilgrimage, because of the Arapaleeswarar temple, which is believed to have a secret path to the Shiva temple in Rasipuram. There is also a temple for Ettukai Amman or Kolli Pavai which is one of the oldest in the town and the place itself derives its name.

The Kolli Hills has 70 hair pin bends to reach the top of the hills. The Kolli Hills are part of the Eastern Ghats, which is a mountain range that runs mostly parallel to the east coast of South India. The mountains are relatively untouched by commercial tourism and still retain their natural beauty.

Apart from its historical significance, the mountains are covered with evergreen forests. The mountains are covered by lush green vegetation in the spring and monsoon, and are streaked with streams which add to the natural beauty. The yoke is still alive in these place.

Kolli Hills has been the top choice for nature lovers, hiking enthusiasts, trekking clubs and meditation practitioners among hill stations in Tamil Nadu. Agaya Gangai is the famous waterfall situated near the Arappaleeswarar temple. Additional sight seeing places in the district are a botanical garden, Telescope House, Boat house, Cave house, New waterfalls called Masila Falls.

Kolli Hills is one of the favourite destination for nature explorers and is a must visit place to enjoy the serene environ.