A skyscraper is a tall continuously habitable building having multiple floors. Modern sources currently define skyscrapers as being at least or in height, though there is no universally accepted definition. Skyscrapers are very tall high-rise buildings. Historically, the term first referred to buildings with between 10 and 20 stories when these types of buildings began to be constructed in the 1880s. Skyscrapers may host offices, hotels, residential spaces, and retail spaces. One common feature of skyscrapers is having a steel frame that supports curtain walls. These curtain walls either bear on the framework below or are suspended from the framework above, rather than resting on load-bearing walls of conventional construction. Some early skyscrapers have a steel frame that enables the construction of load-bearing walls taller than of those made of reinforced concrete. Modern skyscrapers' walls are not load-bearing, and most skyscrapers are characterised by large surface areas of windows made possible by steel frames and curtain walls. However, skyscrapers can have curtain walls that mimic conventional walls with a small surface area of windows. Modern skyscrapers often have a tubular structure, and are designed to act like a hollow cylinder to resist wind, seismic, and other lateral loads. To appear more slender, allow less wind exposure and transmit more daylight to the ground, many skyscrapers have a design with setbacks, which in some cases is also structurally required. , fourteen cities in the world have more than 100 skyscrapers that are or taller: Hong Kong with 518 skyscrapers; Shenzhen, China with 343 skyscrapers; New York City, US with 300 skyscrapers; Dubai, UAE with 237 skyscrapers; Mumbai, India with 208 skyscrapers; Shanghai, China with 180 skyscrapers; Tokyo, Japan with 165 skyscrapers; Guangzhou, China with 152 skyscrapers; Kuala Lumpur, Malaysia with 148 skyscrapers; Chongqing, China, and Chicago, US, both with 135 skyscrapers; Wuhan, China with 109 skyscrapers; and Bangkok, Thailand, and Jakarta, Indonesia, both with 108 skyscrapers. Definition The term "skyscraper" was first applied to buildings of steel-framed construction of at least 10 storeys in the late 19th century, a result of public amazement at the tall buildings being built in major American cities like New York City, Philadelphia, Boston, Chicago, Detroit, and St. Louis. The first steel-frame skyscraper was the Home Insurance Building, originally 10 stories with a height of , in Chicago in 1885; two additional stories were added. Some point to Philadelphia's 10-storey Jayne Building (1849–50) as a proto-skyscraper,