With a total area of 42.7 km2 (16.5 sq mi), New Delhi forms a small part of the Delhi metropolitan area. Because the city is located on the Indo-Gangetic Plain, there is little difference in elevation across the city. New Delhi and surrounding areas were once a part of the Aravalli Range; all that is left of those mountains is the Delhi Ridge, which is also called <answer>the Lungs of Delhi</answer>. While New Delhi lies on the floodplains of the Yamuna River, it is essentially a landlocked city. East of the river is the urban area of Shahdara. New Delhi falls under the seismic zone-IV, making it vulnerable to earthquakes.
The Delhi Ridge is also referred to by what name?
the Lungs of Delhi