With a total area of 42.7 km2, New Delhi forms a small part of the Delhi metropolitan area and is located in the Indo-Gangetic Plain because of which there is little difference in the city's altitude. New Delhi and surrounding areas were once a part of the Aravalli Range, but all that is left now is the Delhi ridge, which is also called the Lungs of Delhi. The second feature is the Yamuna floodplains; New Delhi lies west of the Yamuna river, although for the most part, New Delhi is 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.