The Delhi ridge is an important part of the National Capital Territory (NCT) of the Metropolitan City of Delhi as it forms the extension of the northern side of one of the oldest and ancient Hill Ranges of India called the 'Aravalli Hill Ranges' dating some 1,500 million years ago which is even more ancient than the young 50 million years old Himalayas. The Ridge is also known as the 'Green Lungs' that shelters the capital city from the harsh Desert of Rajasthan from the western portion. It is also shadowed and enveloped with large expanse of greenery that helps in maintaining the natural habitation of wildlife accommodating a variety of animals and birds and hence also maintains a tolerable climate within the city.
The Delhi Ridge is made of quartzite rocks and stretches over a distance of 35 km right from Bhatti Mines towards the Southeast of the 700 years old Tughlaqabad and branching into different directions that finally tapers towards the northern end near Wazirabad which lies on the western banks of Yamuna River.
The Delhi Ridge is divided into four zones which includes the smallest part of the ridge that forms the Northern Ridge denoted by a Hilly zone near the University of Delhi. 425 acres of this Northern Ridge was converted into a Reserved Forest zone in 1915 of which only 217.5 acres exists today due to daily encroachments and illegal construction. Tapering close to the Yamuna River, DDA established the 'Yamuna Biodiversity Park' at Wazirabad that spans over an area of 457 acres and has become one of the most visited Parks in Delhi. It was established as the centre for studying and understanding the potential of nature and the environment along with conserving the natural habitat of Plants. It strives to preserve the 100-year old lost Flora and Fauna which had become extinct at one point in time by establishing numerous wetlands and greenery dotted with a variety of endangered plant species and medicinal herbal plants. This Park can be approached from Bhajanpura in East Delhi, 4 km north of ISBT in South and Central Delhi, Burari in North Delhi and 15 km northeast of Connaught Place.
The second zone is called as the Central Ridge covering a total area of 2,160 acres of land that was also converted into a Reserved Forest area in 1914. It extends from south of Sadar Bazaar up till Dhaula Kuan, however, some of this area is seen encroached with settlements. The third zone is known as the South Central Ridge that lies next to Jawaharlal Nehru University and covers an area of 1,582.5 acres of Green area of which its central portion is converted into the 'Sanjay Van' or 'Sanjay Forest' and the 'Aravalli Biodiversity Park'.
The Aravalli Biodiversity Park and Forest area forms an integral part of South Central zone of the Delhi Ridge section that spans over and area of 692 acres seen with undulating and uneven landscape with outcrops of rocky slopes dotted with Scrub vegetation and Mexican Kikar plantation of the Ridge. Different sizes, shapes and depths of mined pits made of clay are also seen established as wetlands to maintain the moisture and ground water of this Park. The Park is sandwiched between Jawaharlal Nehru University, Mehrauli and Mahipalpur Road, National Highway - 8, Palam Road and Vasant Vihar's Southern borders. The Indian Government of the NCT of Delhi spends large amount of money to maintain this Park and its inhabitants on an annual basis. Unfortunately, most of the surrounding areas of the Forest and the Park are also seen encroached with Settlements. Tourist can approach this Park from the Vasant Vihar - Poorvi Marg Gate that lies about 2 km west of Jawaharlal Nehru University in Munirka or alternatively from the Vasant Kunj Institutional Gate that lies about 1 km west of the Malls in Vasant Kunj and currently with no entry fee but might change after the DDA Conservation work is completed.
The Fourth and last zone is called the Southern Ridge wherein most of the surrounding villages and farmland area are privately owned, however, fortunately it remains one of the least urbanised areas out of the other three zones of the Delhi Ridge in the capital city due to the reserved forest area and wildlife preservation laws. This portion of the Delhi Ridge spans over an area of 15,500 acres of land that was converted into the Asola Bhatti Wildlife Sanctuary in 1986 that merges seamlessly with the Indo-Gigantic Plains of Delhi.
The Asola Bhatti Wildlife Sanctuary forms a perfect place to preserve the ecological heritage of the City. One can spot animals like the rare and almost extinct Blackbuck now only 126 in numbers in Delhi alone, Neelgai or the Blue Bull, Small Indian Mongoose and Common Mongoose, Small Indian Civet, Flying Fox, Jungle Cat, Palm Squirrel, Porcupine, Rufus Tailed Hare, Spiny tailed Lizards and Monitor Lizards along with unique and exotic species of plants, flora and fauna and dense shady and tall trees.
The Asola Bhatti Wildlife Sanctuary is a perfect place for a relaxing, calming and soothing weekend getaway where one can enjoy a rejuvenating nature walk along the undulating 2 km long foot trail which exposes you to the abundant flora and Fauna and the physical attributes of this forest consisting of Hill ranges, species of trees like Balanite and Anogeissus and the 'riparian zone' which is the meeting point of the forest land and a stream allowing you to soak in nature in its truest form. One can also view the mine pits being dug at the Bhatti area to accommodate wetland ecosystem which will help in retaining the moisture of the soil and hence improve the ground water condition of this area. You can enter this sanctuary from the main entrance point near Surajkund area and the other from the Chattarpur and Bhatti area. The entry fee is about INR 50.00 for Indian Nationalities and USD 6.00 for Foreign Nationalities.
Tourists can visit both the Biodiversity Parks between 1000 hours and 1600 hours on all days, however, it is advisable to visit the Asola Bhatti Wildlife Sanctuary preferably between 1000 hours up till noon (any day) but strictly accompanied by a well trained education officer of the Park as the eastern portion of this sanctuary which borders with the Haryana State is filled with the rough and unscrupulous sorts of people who are out to cause trouble from stealing to poaching of the precious blackbucks.