Hanoi is the capital of Vietnam. It covers an area of 3,328.9 square kilometres (1,285 sq mi). With an estimated population of 8.1 million as of 2019, it is the second largest city in Vietnam. The metropolitan area, encompassing nine additional neighbouring provinces, has an estimated population of 16 million. Located in the central area of the Red River Delta, Hanoi is the commercial, cultural, and educational centre of Northern Vietnam. Having an estimated nominal GDP of US$32.8 billion, it is the second most productive economic centre of Vietnam, following Ho Chi Minh City
After the Doi Moi economic policies were approved in 1986, the Communist Party and national and municipal governments hoped to attract international investments for urban development projects in Hanoi. The high-rise commercial buildings did not begin to appear until ten years later due to the international investment community being skeptical of the security of their investments in Vietnam. Rapid urban development and rising costs displaced many residential areas in central Hanoi. Following a short period of economic stagnation after the 1997 Asian financial crisis, Hanoi resumed its rapid economic growth.
On 29 May 2008, it was decided that Hà Tây Province, Vĩnh Phúc Province's Mê Linh District and 4 communes of Lương Sơn District, Hòa Bình Province be merged into the metropolitan area of Hanoi from 1 August 2008. Hanoi's total area then increased to 334,470 hectares in 29 subdivisions with the new population being 6,232,940.,effectively tripling its size. The Hanoi Capital Region (Vùng Thủ đô Hà Nội), a metropolitan area covering Hanoi and 6 surrounding provinces under its administration, will have an area of 13,436 square kilometres (5,188 sq mi) with 15 million people by 2020.
Hanoi has experienced a rapid construction boom recently. Skyscrapers, popping up in new urban areas, have dramatically changed the cityscape and have formed a modern skyline outside the old city. In 2015, Hanoi is ranked 39th by Emporis in the list of world cities with most skyscrapers over 100 m; its two tallest buildings are Hanoi Landmark 72 Tower (336 m, second tallest in Vietnam after Ho Chi Minh City's Landmark 81 and third tallest in south-east Asia after Malaysia's Petronas Towers) and Hanoi Lotte Center (272 m, also, third tallest in Vietnam).
Public outcry in opposition to the redevelopment of culturally significant areas in Hanoi persuaded the national government to implement a low-rise policy surrounding Hoàn Kiếm Lake. The Ba Đình District is also protected from commercial redevelopment.