Chicago is the largest city by population in the state of Illinois and the Midwest, and a dominant center of finance, industry and culture in the region. The city was long the "second city" (second in population to New York), and is currently the third-most populous city in the United States, with nearly 3 million people. The Chicago metropolitan area (commonly referred to as Chicagoland) has a population of over 9.7 million people in Illinois, Wisconsin and Indiana, making it also the third largest metropolitan area in the U.S. Adjacent to Lake Michigan, it is among the world's twenty-five largest urban areas by population. Loughborough University classifies Chicago as an alpha world city for its worldwide economic influence.(from wikipedia)
The City Hall rooftop garden sits atop Chicago's City Hall, an 11-story office building in Chicago's Loop. City Hall and the adjacent Cook County building appear to most people as one building spanning a city block bounded by LaSalle, Randolph, Clark and Washington streets. First planted in 2000, the City Hall rooftop garden was conceived as a demonstration project - part of the City's Urban Heat Island Initiative - to test the benefits of green roofs and how they affect temperature and air quality. The garden consists of 20,000 plants of more than 100 species, including shrubs, vines and two trees. The plants were selected for their ability to thrive in the conditions on the roof, which is exposed to the sun and can be windy and arid. Most are prairie plants native to the Chicago region.