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The CN Tower ((フランス語:Tour CN)) is a concrete communications and observation tower in downtown Toronto, Ontario, Canada.〔 Built on the former Railway Lands, it was completed in 1976, becoming the world's tallest free-standing structure and world's tallest tower at the time. It held both records for 34 years until the completion of Burj Khalifa and Canton Tower in 2010. It is now the 3rd tallest tower in the world and remains the tallest free-standing structure in the Western Hemisphere, a signature icon of Toronto's skyline, and a symbol of Canada,〔(The CN Tower is Dead. Long Live The CN Tower! ), The Torontoist, September 4, 2007. (retrieved on November 17, 2008).〕〔(CN Tower celebrates 30th birthday ), Broadcast News/canada.com, June 26, 2006〕 attracting more than two million international visitors annually.〔 Its name "CN" originally referred to Canadian National, the railway company that built the tower. Following the railway's decision to divest non-core freight railway assets, prior to the company's privatization in 1995, it transferred the tower to the Canada Lands Company, a federal Crown corporation responsible for real estate development. Since the name ''CN Tower'' became common in daily usage, the abbreviation was eventually expanded to Canadian National Tower or Canada's National Tower. However, neither of these names is commonly used.〔(【引用サイトリンク】title= Canada's Wonder of the World )〕 In 1995, the CN Tower was declared one of the modern Seven Wonders of the World by the American Society of Civil Engineers. It also belongs to the World Federation of Great Towers, where it holds second-place ranking.〔(【引用サイトリンク】url=http://www.infoplease.com/ipa/A0923082.html )〕〔(【引用サイトリンク】url=http://www.great-towers.com/towers/cn-tower/ )〕 == History == The idea of the CN Tower originated in 1968 when the Canadian National Railway wanted to build a large TV and radio communication platform to serve the Toronto area, as well as demonstrate the strength of Canadian industry and CN in particular. These plans evolved over the next few years, and the project became official in 1972. The tower would have been part of Metro Centre (see CityPlace), a large development south of Front Street on the Railway Lands, a large railway switching yard that was being made redundant by newer yards outside the city. Key project team members were NCK Engineering as structural engineer; John Andrews Architects; Webb, Zerafa, Menkes, Housden Architects; Foundation Building Construction; and Canron (Eastern Structural Division).〔〔〔 As Toronto grew rapidly during the late 1960s and early 1970s, multiple skyscrapers were constructed in the downtown core, most notably First Canadian Place. The reflective nature of the new buildings compromised the quality of broadcast signals necessitating new, higher antennas that were at least tall. At the time, most data communications took place over point-to-point microwave links, whose dish antennae covered the roofs of large buildings. As each new skyscraper was added to the downtown, former line-of-sight links were no longer possible. CN intended to rent "hub" space for microwave links, visible from almost any building in the Toronto area. The CN Tower can be seen from at least as far away as Kennedy Street in Aurora, Ontario, approximately to the north, east of Toronto, in Oshawa, and from several points on the south shore of Lake Ontario, to the south in the U.S. state of New York.〔〔 The original plan for the tower envisioned a tripod consisting of three independent cylindrical "pillars" linked at various heights by structural bridges. Had it been built, this design would have been considerably shorter, with the metal antenna located roughly where the concrete section between the main level and the SkyPod lies today. As the design effort continued, it evolved into the current design with a single continuous hexagonal core to the SkyPod, with three support legs blended into the hexagon below the main level, forming a large Y-shape structure at the ground level.〔 The idea for the main level in its current form evolved around this time, but the Space Deck (now named SkyPod) was not part of the plans until some time later. One engineer in particular felt that visitors would feel the higher observation deck would be worth paying extra for, and the costs in terms of construction were not prohibitive. It was also some time around this point that it was realized that the tower could become the world's tallest structure, and plans were changed to incorporate subtle modifications throughout the structure to this end.〔〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「CN Tower」の詳細全文を読む スポンサード リンク
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