Question: What is the total area, in square miles, of the Indian city that's the headquarters of the Northern Railway?

full_context: Document 1: Hyderabad: The most commonly used forms of medium distance transport in Hyderabad include government owned services such as light railways and buses, as well as privately operated taxis and auto rickshaws. Bus services operate from the Mahatma Gandhi Bus Station in the city centre and carry over 130 million passengers daily across the entire network.:76 Hyderabad's light rail transportation system, the Multi-Modal Transport System (MMTS), is a three line suburban rail service used by over 160,000 passengers daily. Complementing these government services are minibus routes operated by Setwin (Society for Employment Promotion & Training in Twin Cities). Intercity rail services also operate from Hyderabad; the main, and largest, station is Secunderabad Railway Station, which serves as Indian Railways' South Central Railway zone headquarters and a hub for both buses and MMTS light rail services connecting Secunderabad and Hyderabad. Other major railway stations in Hyderabad are Hyderabad Deccan Station, Kachiguda Railway Station, Begumpet Railway Station, Malkajgiri Railway Station and Lingampally Railway Station. The Hyderabad Metro, a new rapid transit system, is to be added to the existing public transport infrastructure and is scheduled to operate three lines by 2015.
Document 2: Indo-Gangetic Plain: The Indo-Gangetic Plain, also known as the Indus-Ganga Plain and the North Indian River Plain, is a 630-million-acre (2.5-million km2) fertile plain encompassing northern regions of the Indian subcontinent, including most of northern and eastern India, the eastern parts of Pakistan, virtually all of Bangladesh and southern plains of Nepal.  The region is named after the Indus and the Ganges rivers and encompasses a number of large urban areas. The plain is bound on the north by the Himalayas, which feed its numerous rivers and are the source of the fertile alluvium deposited across the region by the two river systems. The southern edge of the plain is marked by the Chota Nagpur Plateau. On the west rises the Iranian Plateau.
Document 3: New Delhi: New Delhi is a major junction in the Indian railway network and is the headquarters of the Northern Railway. The five main railway stations are New Delhi railway station, Old Delhi, Nizamuddin Railway Station, Anand Vihar Railway Terminal and Sarai Rohilla. The Delhi Metro, a mass rapid transit system built and operated by Delhi Metro Rail Corporation (DMRC), serves many parts of Delhi and the neighbouring cities Faridabad, Gurgaon, Noida and Ghaziabad. As of August 2011, the metro consists of six operational lines with a total length of 189 km (117 mi) and 146 stations, and several other lines are under construction. It carries millions of passengers every day. In addition to the Delhi Metro, a suburban railway, the Delhi Suburban Railway exists.
Document 4: New Delhi metro station: New Delhi is a station on the Yellow Line of the Delhi Metro. It is within walking distance from the Indian Railways New Delhi station. It is on the Ajmeri Gate (Platform Number 16) side of the New Delhi Railway Station.
Document 5: New Delhi: New Delhi has one of India's largest bus transport systems. Buses are operated by the state-owned Delhi Transport Corporation (DTC), which owns largest fleet of compressed natural gas (CNG)-fueled buses in the world. Personal vehicles especially cars also form a major chunk of vehicles plying on New Delhi roads. New Delhi has the highest number of registered cars compared to any other metropolitan city in India. Taxis and Auto Rickshaws also ply on New Delhi roads in large numbers. New Delhi has one of the highest road density in India.
Document 6: Hazrat Nizamuddin railway station: Nizamuddin हज़रत निज़ामुद्दीन Rapid transit, Light rail, Commuter rail & Regional rail station Location New Delhi, Delhi India 28 ° 35 ′ 21 ''N 77 ° 15 ′ 15'' E ﻿ / ﻿ 28.58917 ° N 77.25417 ° E ﻿ / 28.58917; 77.25417 Elevation 206.7 metres (678 ft) Platforms 7 Construction Structure type Standard (on ground station) Parking Yes Other information Status Functioning Station code NZM Zone (s) Northern Railway zone Division (s) Delhi Electrified Yes Traffic Passengers (Daily) 360,000 + Location Nizamuddin Location within Delhi
Document 7: Urban rail transit in India: There are currently 11 operational rapid transit (also called 'metro') systems in ten cities in India. As of November 2017, India has 425 kilometres (264 miles) of operational metro lines and 347 stations. A further 500 + km of lines are under construction. Metro rail lines in India are composed of mainly standard gauge. Projects like the Kolkata Metro and Delhi Metro used broad gauge for their earliest lines but all new projects in India are on standard gauge as rolling stock imported is of standard gauge.
Document 8: Delhi: Delhi Union territory and Megacity National Capital Territory of Delhi From top clockwise: Lotus temple, Humayun's Tomb, Connaught Place, Akshardham temple and India Gate Location of Delhi in India Coordinates: 28 ° 36 ′ 36 ''N 77 ° 13 ′ 48'' E ﻿ / ﻿ 28.61000 ° N 77.23000 ° E ﻿ / 28.61000; 77.23000 Coordinates: 28 ° 36 ′ 36 ''N 77 ° 13 ′ 48'' E ﻿ / ﻿ 28.61000 ° N 77.23000 ° E ﻿ / 28.61000; 77.23000 Country India Settled 6th century B.C. Incorporated 1857 Capital formation 1911 Formation of Union Territory 1956 Formation of NCT 1 February 1992 Capital New Delhi Districts 11 Government Body Government of Delhi Lt. Governor Anil Baijal, IAS Chief Minister Arvind Kejriwal (AAP) Deputy Chief Minister Manish Sisodia Chief Secretary Anshu Prakash, IAS Commissioner of Police Amulya Patnaik, IPS Area Union territory 1,484.0 km (573.0 sq mi) Water 18 km (6.9 sq mi) Area rank 31st Elevation 200 -- 250 m (650 -- 820 ft) Population (2011) Union territory 16,787,941 Density 11,312 / km (29,298 / sq mi) Urban 16,349,831 (2nd) Megacity 11,034,555 (2nd) Metro (2016) 26,454,000 (1st) Demonym (s) Delhiite Languages Official Hindi English Additional official Punjabi Urdu GDP Nominal (NCT) ₹6.86 lakh crore (US $100 billion) (2017 - 18) Nominal per capita ₹329,093 (US $4,800) (2017 - 18) Metro GDP / PPP $167 -- 370 billion Time zone IST (UTC + 5.30) Pincode (s) 1100XX Area code (s) + 91 11 ISO 3166 code IN - DL Website delhi.gov.in
Document 9: New Delhi: 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 the Lungs of Delhi. 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.
Document 10: Hyderabad: Situated in the southern part of Telangana in southeastern India, Hyderabad is 1,566 kilometres (973 mi) south of Delhi, 699 kilometres (434 mi) southeast of Mumbai, and 570 kilometres (350 mi) north of Bangalore by road. It lies on the banks of the Musi River, in the northern part of the Deccan Plateau. Greater Hyderabad covers 650 km2 (250 sq mi), making it one of the largest metropolitan areas in India. With an average altitude of 542 metres (1,778 ft), Hyderabad lies on predominantly sloping terrain of grey and pink granite, dotted with small hills, the highest being Banjara Hills at 672 metres (2,205 ft). The city has numerous lakes referred to as sagar, meaning "sea". Examples include artificial lakes created by dams on the Musi, such as Hussain Sagar (built in 1562 near the city centre), Osman Sagar and Himayat Sagar. As of 1996, the city had 140 lakes and 834 water tanks (ponds).
Document 11: New Delhi: New Delhi (i/ˌnjuː ˈdɛli/) is a municipality and district in Delhi which serves as the capital and seat of government of India. In addition, it also serves as the seat of Government of Delhi.
Document 12: New Delhi: New Delhi lies on several fault lines and thus experiences frequent earthquakes, most of them of mild intensity. There has, however, been a spike in the number of earthquakes in the last six years, most notable being a 5.4 magnitude earthquake in 2015 with its epicentre in Nepal, a 4.7-magnitude earthquake on 25 November 2007, a 4.2-magnitude earthquake on 7 September 2011, a 5.2-magnitude earthquake on 5 March 2012, and a swarm of twelve earthquakes, including four of magnitudes 2.5, 2.8, 3.1, and 3.3, on 12 November 2013.
Document 13: New Delhi: The Delhi Metro is a rapid transit system serving New Delhi, Delhi, Gurgaon, Faridabad, Noida, and Ghaziabad in the National Capital Region of India. Delhi Metro is the world's 12th largest metro system in terms of length. Delhi Metro was India's first modern public transportation system, which had revolutionised travel by providing a fast, reliable, safe, and comfortable means of transport. The network consists of six lines with a total length of 189.63 kilometres (117.83 miles) with 142 stations, of which 35 are underground, five are at-grade, and the remainder are elevated. All stations have escalators, elevators, and tactile tiles to guide the visually impaired from station entrances to trains. It has a combination of elevated, at-grade, and underground lines, and uses both broad gauge and standard gauge rolling stock. Four types of rolling stock are used: Mitsubishi-ROTEM Broad gauge, Bombardier MOVIA, Mitsubishi-ROTEM Standard gauge, and CAF Beasain Standard gauge.
Document 14: New Delhi: Although colloquially Delhi and New Delhi as names are used interchangeably to refer to the jurisdiction of NCT of Delhi, these are two distinct entities, and the latter is a small part of the former.
Document 15: Delhi: Delhi Union territory and Megacity National Capital Territory of Delhi From top clockwise: Lotus temple, Humayun's Tomb, Connaught Place, Akshardham temple and India Gate Location of Delhi in India Coordinates: 28 ° 36 ′ 36 ''N 77 ° 13 ′ 48'' E ﻿ / ﻿ 28.61000 ° N 77.23000 ° E ﻿ / 28.61000; 77.23000 Coordinates: 28 ° 36 ′ 36 ''N 77 ° 13 ′ 48'' E ﻿ / ﻿ 28.61000 ° N 77.23000 ° E ﻿ / 28.61000; 77.23000 Country India Settled 6th century B.C. Incorporated 1857 Capital formation 1911 Formation of Union Territory 1956 Formation of NCT 1 February 1992 Capital New Delhi Districts 11 Government Body Government of Delhi Lt. Governor Anil Baijal, IAS Chief Minister Arvind Kejriwal (AAP) Chief Secretary Anshu Prakash, IAS Commissioner of Police Amulya Patnaik, IPS Area Union territory 1,484.0 km (573.0 sq mi) Water 18 km (6.9 sq mi) Area rank 31st Elevation 200 -- 250 m (650 -- 820 ft) Population (2011) Union territory 16,787,941 Density 11,312 / km (29,298 / sq mi) Urban 16,349,831 (2nd) Megacity 11,034,555 (2nd) Metro (2016) 26,454,000 (1st) Demonym (s) Delhiite Languages Official Hindi and English Additional official Punjabi and Urdu Time zone IST (UTC + 5.30) Pincode (s) 1100XX Area code (s) + 91 11 ISO 3166 code IN - DL Metro GDP (PPP) $167 to $370 billion Website delhi.gov.in
ground_truth: 16.5 sq mi
sub_queries: What Indian city is the headquarters of the Northern Railway? Answer: New Delhi
What is the total area of New Delhi in square miles? Answer: 16.5 sq mi