As per Census 2001, t he population of the Kolli Hills is 36852. There are 14 village panchayats and 275 hamlets. The population predominantly consists of scheduled tribes called Hindu Malayali whose spoken language is only Tamil. In two pockets SC population is found which is around 700.
Cultivation of Jack Fruit, Guvava, Hill Banana, Pineapple, Pepper, Coffee, Cardamom,topioca, honey and rice are the main agricultural activities.
The government reserve forests are seen in Ariyur, Puliyan Solai, Selur and Vazhavandhi Nadu. An area of 200 hectares is in the process of reforestation. Tigers and elephants which were once common in it are now extinct; only small animals such as black bears, hares, porcupines, and wild dogs are seen.
Legends have it that the hills were part of the famous Madhuvanam (Honey Forest) reserved by Sugriva of the epic Ramayana. The Maximum elevation ranges from 3500' to 4500' with the tallest peak Vettakaramalai, is rising to 4663' above sea level.
The hills formed a natural boundary between the Kongu Nadu and Chola Nadu. At the beginning of the Christian era the Mountain and its habitants were rules by Mazhavars and the King Vaivil Ori ws much celebrated among them. Legends have it that he was a great archer and released a arrow by him pierced first and elephant, then went through the open mouth of a tiger, then a deer and the a pig and then hit a monitor lizard killing instantaneously all. A statue was erected to honour the king in 1975 by Thiru Kalaingar M. Karunanidhi, Honorouble Chief Minister of Tamil Nadu and the Government sponsored festival (VALVIL ORI VIZHA) every year named after him. Apart from known abode of the Saints, the Buddhists, the Jains set up a number of retreats, those fell prey to time. A stone image of Theerthangar reminds the existence of the earlier Jain influence. The famous Shiva Temple called Arappalleeswarar Temple dating back to 12th century situates at periakoviloor near the famous water falls Akasa Gangai. Reportedly an ancient and powerful deity called Kolli Paavai of Ettukkai Amman is also at Kolli Hills. It attracts large pilgrims on fiew moon days originally a Jain retreat.
The glory of Kolli Hills and the Charity of the King Valvil Ori is liberally sung by the Sangam literature like Agananooru, Purananooru, Kurunthogai, Pathitrupathu and Natrinai.
Numerous streams originate from Kolli Hills. The major rivers traversing the hills are Aiyar, Varattar etc.
At present Kolli Hills could be reached through a ghat road which was 70 hairpins bends. The village at the foot hill is Karavalli.. From Namakkal to Kolli Hills the distance is 55 KMs.. The ghat road alone 26 KMs. The district administration taking steps to form an another ghat road called Nariankadu-Mullukurichi road which, when formed will have only 2-3 hairpin bends.
For the convenience of the tourists the Panchayat Union has constructed six cottage at Semmedu. At near Arapaleeswarar Temple an Youth Hostel is also available which could accommodate up to 30 persons. This could also be used as a training center. An excellent lawn and a rose garden greets the visitors. The inmates can avail the tasty Kollihill food supplied from the canteen run by the Women Self Help Group. All these accommodations are available fro rent from the Commissioner, Kollimalai Panchayat Union, Semmedu (Phone No. 04286 247425). Apart from these at present two private lodges with boarding facilities are available.