Delhi Ridge, sometimes simply called The Ridge, is a ridge in the National Capital Territory of Delhi in India. The ridge is a northern extension of the ancient Aravalli Range, some 1500 million years old (compared to just 50 million for the Himalaya). The ridge consists of quartzite rocks and extends from the Southeast at Tughlaqabad, near the Bhatti mines, branching out in places and tapering off in the north near Wazirabad on the west bank of the river Yamuna, covering a distance of about 35 kilometers.
The Delhi Ridge is said to be the green lungs for the city and protects Delhi from the hot winds of the deserts of Rajasthan to the west. It is also responsible for earning Delhi the tag of the World's Second most bird-rich Capital city after Kenya's Nairobi.
The Ridge today, for administrative reasons, is divided into 4 separate zones, namely:
- The Old Delhi or Northern Ridge denotes the hilly area near Delhi University and is by far the smallest segment of the Ridge. Nearly 170 hectares were declared a Reserved Forest in 1915. Less than 87 hectares remain today, which is slated to develop as Biodiversity Park by the Delhi Development Authority.
- The New Delhi or Central Ridge was made into a Reserved Forest in 1914 and stretches from just south of Sadar Bazaar to Dhaula Kuan. It extends over 864 hectares, but some bits have been nibbled away.
- The Mehrauli or South-Central Ridge is centred on "Sanjay Vana", near JNU and Vasant Kunj, and encompasses 633 hectares. Large chunks have been encroached and built upon.
- The Tughlaqabad or Southern Ridge sprawls across 6200 hectares and includes the Asola Bhatti Wildlife Sanctuary. This is the least urban of the 4 segments of the Ridge, but a lot of it is village-owned or privately owned farmland.
In 1993, parts of north Delhi, central Delhi, south West Delhi and south Delhi covering 7,777 hectares was declared a reserve forest. Thereafter in 1994 and 1996, a major part of the ridge was notified by the Government, thus stopping all construction.
Over the years, pressures of urban development, have seen forests of Delhi ridge under threat. In many areas, landscaped public parks, and public housing have come up, plus the area also faces dumping of construction waste.
Aravali Biodiversity Park
The Aravali Biodiversity Park  is an area spreading over 692 acres (2.80 km2) on the South Central Delhi Ridge within the Aravalli Range. The area is confined by JNU, the Mehrauli - Mahipalpur road, NH-8 and the Palam road and the southern boundary of Vasant Vihar, Delhi. Delhi Development Authority and University of Delhi under a joint programme, Biodiversity Parks Programme maintains the area. Every year a substantial amount of money is spent in restoration, development and maintenance.
The Land under Aravali Bio diversity Park was once a site for mining. Martha Shinde (Scindias) had a mining lease for the 2.3 km² area. They plundered out whatever they could. For years Shinde exploited forest resources including minerals, mica, sand, stone, rocks and water. Land, which once was covered with a dense forest, soon turned into pits and hillocks. A systematic planting program is carried out and every year native trees and bushes are planted to remove unwanted weeds, i.e. Prosopis juliflora. Scientists from Centre for Environmental Management of Degraded Ecosystems, University of Delhi have so far got over 10 ecosystems reintroduced with over 40 biotic communities. Portions of Aravali, which comes under Gujarat, are covered with natural dense forest. However, The land on which Aravali Biodiversity Park is being developed, was devoid of such natural growth of forest due to extensive mining of the area. Center for Environment Management & Degraded Ecosystem (Delhi University) works closely with Delhi Development Authority and has plans to revive native flora and Fauna of Aravalli hill ranges. Planting of native species like Dhau (Anogeissus pendula), Babul (Acacia nilotica), Kair (Capparis decidua),and Dhak (Butea monosperma)etc. has been carried out. A Rangeland with native grasses has been developed. A Conservatory of Butterflies, orchidarium and fernary has been developed.
It is believed that Aravallis are one of the oldest mountain ranges in India which evolved around 1500 million years ago. Range extends from Gujarat through Rajasthan to Haryana-Delhi. In Delhi the spurs of the Aravallis are commonly called as the Delhi Ridge which is divided into the Northern, Central, South Central and Southern Ridge. The Aravali Biodiversity Park on Gurgaon-Delhi border, developed by the Municipal Corporation of Gurgaon was inaugurated on June 5, 2010, World Environment Day 
Historical monuments in North Ridge
Ashoka pillar, brought to Delhi by Firuz Shah Tughluq in 1356.
Pir Ghaib, a 14th-century hunting lodge and Observatory built by Feroz Shah Tughlaq
- Bindhy Wasini Pandey, Natural Resource Management, Mittal Publications, 2005, ISBN 978-81-7099-986-7, "... The Ridge and its neighbouring hilly tracts represent the natural flora. The major natural forests in Delhi are generally restricted to the Ridge. The natural flora is a tropical, thorny and secondary forest. The greater of the reserved ..."
- Geological Survey of India, Records of the Geological Survey of India, Volumes 5-7, Government of India, 1872, "... These ridges are prolongations of the Aravali mountain system, and are approximately on the line of the Indo-gangetic watershed ..."
- Lindsay Brown, Amelia Thomas, Rajasthan, Delhi and Agra, Lonely Planet, 2008, ISBN 978-1-74104-690-8, "... Delhi lies on the vast flatlands of the Indo-Gangetic Plain, though the northernmost pimples of the Aravallis amount to the Ridge, which lies west of the city centre ..."
- "Delhi Ridge". Parks and Gardens in Delhi. IndFY.com. Retrieved 2006-12-23.
- "Geology Details". rainwaterharvesting.com. Centre for Science and Environment. Retrieved 2006-12-23.
- "Trees of Dellhi". Dorling Kindersley.
- Darpan Singh (September 4, 2013). "Govt assures to demarcate Delhi ridge boundaries by mid-October". Hindustan Times. Retrieved 2013-09-10.
- Darpan Singh (September 3, 2013). "Forest dept prepares plan to save the Delhi ridge". Hindustan Times. Retrieved 2013-09-10.
- Shivani Singh (September 9, 2013). "Land rush spoils Delhi’s enviable green records". Hindustan Times. Retrieved 2013-09-10.
- Aravali Bio-Diversity Park Curtain Raising On World Environment Day June 05 2010 Municipal Corporation of Gurgaon.
- "Flagstaff Tower, Old Delhi.". victorianweb.org. Retrieved 5 September 2012.
- "Flagstaff Tower - Northern Ridge, Delhi". Indian Express, Expresstravel. Retrieved 5 September 2012.
- Kalpavriksh (1991). The Delhi Ridge Forest. Decline and Conservation.
|Wikimedia Commons has media related to Delhi Ridge.|
- Aravali Biodiversity Park, Gurgaon, website
- Foundation of biodiversity park laid
- Thorny British tree to be thrown out of biodiversity park
- ARAVALLI BIODIVERSITY PARK