The CN Tower

T tallest standing structure North America. Y glass elevator p. T incredible there glass floor, which y scary . There revolving restaurant which offers spectacular views y.

T CN Tower, located downtown Toronto, Ontario, Canada, communications tourist tower standing 553.33 metres (1,815.39 ) . I surpassed height Ostankino Tower while still under construction 1975, becoming tallest -standing structure world. O September 12, 2007, after holding record 31 years, CN tower surpassed height y still-under-construction Bj Dubai. I remains tallest -standing structure Americas signature Toronto's skyline, attracting million international visitors annually.

CN originally referred Canadian National, railway company built tower. Following railway's decision divest - freight railway assets, prior company's privatization 1995 transferred tower Canada Lands Company, federal Crown corporation responsible estate development. Since local residents wished retain CN Tower, abbreviation expand Canada's National Tower rather original Canadian National Tower; however, neither these commonly .

I 1995, CN Tower declared modern Seven Wonders World y American Society Civil Engineers. I belongs World Federation Great Towers.

T concept CN Tower originated 1968 Canadian National Railway desire build large TV radio communication platform serve Toronto area, demonstrate strength Canadian industry CN particular. These plans evolved x years, project became official 1972. T tower would p Metro Centre ( CityPlace), large development south Front Street Railway Lands, large railway switching y being redundant y newer yards outside y. Ky project members NCK Engineering structural engineer; J Andrews Architects; Webb, Zerafa, Menkes, Housden Architects; Foundation Building Ctruction; Canron (Eastern Structural Division).

A time, Toronto town, 1960s early 1970s construction numerous large skyscrapers downtown . T broadcasting downtown y difficult reflections buildings. T y solution would raise antennas above buildings, demanding tower 300 metres (984 ) . Additionally, time, communications place point--point microwave links, whose antennae covered roofs large buildings. A skyscraper added downtown, former --sight links longer possible. CN intended "hub" space microwave links, visible almost y building Toronto . T CN Tower least y Gamble Street Richmond Hill, Ontario, approximately 30 kilometres (19 ) north, several points south shore L Ontario, 48 kilometres (30 ) south.

T original p tower envisioned tripod consisting three independent cylindrical "pillars" linked various heights y structural bridges. H built, design would considerably shorter, metal antenna located roughly where concrete section between level Sy P today. A design effort continued, evolved current design single continuous hexagonal Sy P, three support g blended hexagon below level, forming large Y-shape structure ground level.

T level current evolved around time, Sy P p plans until later. O engineer particular visitors would higher observation would worth paying extra , costs terms construction prohibitive. I around point realized tower could become world's tallest structure, plans changed incorporate subtle modifications throughout structure .

Construction CN Tower began February 6, 1973 massive excavations tower foundation. By foundation complete, 56,000 tonnes (61,729 short ) shale removed depth 15 metres (49.2 ) centre, incorporating 7,000 cubic metres (9,156 y) concrete 450 tonnes (496 short ) rebar 36 tonnes (40 short ) steel cable built thickness 6.7 metres (22 ). T portion construction fairly rapid, y months needed between start foundation being ready construction p.

T build support pillar, hydraulically-raised slipform built . T fairly impressive engineering , consisting large metal platform raised itself jacks about 6 metres (19.7 ) p y concrete below . Concrete poured continuously y 1,532 people until February 22, 1974, during which already become tallest structure Canada, surpassing recently built I Superstack, which built using similar methods. I total, tower contains 40,500 cubic metres (52,972 y) concrete, which mixed - order ensure batch consistency. Through pour, vertical accuracy tower maintained y comparing p form's location massive plumb- hanging , observed y small telescopes ground. O height tower, varies vertical accuracy y y 29 millimetres (1.1 ).

I August 1974, construction level commenced. Using 45 hydraulic jacks attached cables strung temporary steel crown anchored p tower, twelve giant steel wooden bracket forms slowly raised, ultimately taking about crawl p their final position. These forms create brackets support level, construction level itself. T Sy P built concrete poured wooden frame attached rebar lower level deck, reinforced large steel compression around outside.

T antenna originally raised y crane well, during construction Sikorsky S-64 Skycrane helicopter became available United States Ay theirs civilian operators. T helicopter, named "Olga", first remove crane, antenna p 36 sections. T flights antenna pieces minor tourist attraction their , schedule printed local newspapers. U helicopter saved months construction time, phase taking y three weeks instead planned x months. T tower topped April 2, 1975 after 26 months construction, officially capturing height record Moscow's Ostankino Tower, bringing total 118,000 tonnes (130,073 ).

T years construction, plans Metro Centre scrapped, leaving tower isolated Railway Lands largely abandoned light-industrial space. T caused serious problems tourists access tower. N Baldwin, project architect J Andrews, wrote "A logic which dictated design lower accommodation upset," "Under ludicrous circumstances Canadian National would hardly chosen location build."