System, and white flight from urban cores to rapidly expanding suburbs. Due to well-intended but ineptly executed urban revitalization projects, downtowns eventually came to be dominated by high-rise office buildings in which commuters from the suburbs filled white-collar jobs, while the remaining residential populations sank further into unemployment, poverty, and homelessness. By the 1990s, many office-oriented businesses began to abandon the tired old downtowns for the suburbs, resulting in what are now known as "edge cities". One textbook, in explaining why edge cities are so popular, stated: Since then, between 2000 and 2010, downtown areas grew rapidly in population. In U.S. metro areas with at least five million people, the population within two miles of the city hall grew twice as fast as the overall population in the metro area. Relative geography The terms downtown and uptown can refer to cardinal directions, for example, in Manhattan, where downtown is also a relative geographical term. Anything south of where the speaker is currently standing, in most places, is said to be downtown. Anything north of the speaker is uptown. In the common New York City phrase "We're going to take the subway downtown", downtown refers to traveling in the geographic direction of south. A person standing on 121st Street and walking ten blocks south could also be said to have walked ten blocks downtown. The term uptown is used to refer to the cardinal direction north. Such concepts derive from Manhattan's elongated shape, running roughly north–south and nowhere more than wide. As such, transportation on the island travels in the uptown/downtown directions. The other boroughs are wider, and "downtown" there refers to Lower Manhattan, Downtown Brooklyn, or some more local business district. Mercantile efforts to promote the South Bronx as "Downtown Bronx" have met with little success. In some North American cities, downtown is the formal name of the neighborhood in which the city's central business district is located. Most major North American cities are located on major bodies of water, like oceans, lakes, and rivers. As cities expanded, people built further away from the water and their historical cores, often uphill. Thus the central business district of a North American city, or the historical core of the city, is often located "down", in altitude, relative to the remainder of the city. Many cities use the Manhattan model and continue to use downtown, midtown, and uptown both as informal relative geographical