TheCN Tower (French:Tour CN) is a 553.3 m-high (1,815.3 ft) communications and observationtower inToronto, Ontario, Canada.[3][8] Completed in 1976, it is located indowntown Toronto, built on the formerRailway Lands. Its name "CN" refers toCanadian National, the railway company that built the tower. Following the railway's decision todivest non-core freight railway assets prior to the company'sprivatization in 1995, it transferred the tower to theCanada Lands Company, a federalCrown corporation responsible for the government's real estate portfolio.
It is a signature icon of Toronto'sskyline[15][16] and attracts more than two million international visitors annually.[5][17] It houses several observation decks, a revolving restaurant at some 350 metres (1,150 ft), and an entertainment complex.[18]
History
The original concept of the CN Tower was first conceived in 1968 when the Canadian National Railway wanted to build a large television and radio communication platform to serve the Toronto area, and to 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 (seeCityPlace), a large development south ofFront Street on theRailway Lands, a large railway switching yard that was being made redundant after the opening of theMacMillan Yard north of the city in 1965 (then known as Toronto Yard). 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).[3][4][8]
As Toronto grew rapidly during the late 1960s and early 1970s, multiple skyscrapers were constructed in the downtown core, most notablyFirst Canadian Place, which housesBank of Montreal's head offices. The reflective nature of the new buildings reduced the quality of broadcast signals, requiring new, higher antennas that were at least 300 m (980 ft) tall. The radio wire is estimated to be 102 metres (335 ft) long in 44 pieces, the heaviest of which weighs around 8 tonnes (8.8 short tons; 7.9 long tons).[19]
At the time, most data communications took place overpoint-to-point microwave links, whose dish antennas 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 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 Top lies today. As the design effort continued, it evolved into the current design with a single continuous hexagonal core to The Top, with three support legs blended into the hexagon below the main level, forming a large Y-shape structure at the ground level.[8][20]
The idea for the main level in its current form evolved around this time, but the Space Deck (currently named The Top, and originally dubbed 'Bud's Bubble' named after Bud Andrews) was not part of the plans until later. Bud Andrews (president of the Metro Centre Developments Group) 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. Also around this time, it was realized that the tower could become the world's tallest free-standing structure to improve signal quality and attract tourists, and plans were changed to incorporate subtle modifications throughout the structure to this end.[8][20]
Construction
Map of the area immediately surrounding CN Tower shortly before the opening ofRipley's Aquarium of Canada in 2013
The CN Tower was built byFoundation Company of Canada with Canron of Etobicoke handling the steel and antenna fabrication work.
Construction began on February 6, 1973, with massive excavations at the tower base for the foundation. By the time the foundation was complete, 56,000 t (62,000short tons; 55,000long tons) ofearth andshale were removed to a depth of 15 m (49.2 ft) in the centre, and a base incorporating 7,000 m3 (9,200 cu yd) of concrete with 450 t (496 short tons; 443 long tons) ofrebar and 36 t (40 short tons; 35 long tons) ofsteel cable had been built to a thickness of 6.7 m (22 ft). This portion of the construction was fairly rapid, with only four months needed between the start and the foundation being ready for construction on top.[20]
To create the main support pillar, workers constructed a hydraulically raisedslipform at the base. This was a fairly unprecedented engineering feat on its own, consisting of a large metal platform that raised itself on jacks at about 6 m (20 ft) per day as the concrete below set. Concrete was poured Monday to Friday (not continuously) by a small team of people until February 22, 1974, at which time it had already become the tallest structure in Canada, surpassing the recently built 381-metre (1,250 ft) tallInco Superstack inSudbury, built using similar methods.
The tower contains 40,500 m3 (53,000 cu yd) of concrete, all of which was mixed on-site in order to ensure batch consistency. Through the pour, the vertical accuracy of the tower was maintained by comparing the slip form's location to massiveplumb bobs hanging from it, observed by small telescopes from the ground. Over the height of the tower, it varies from true vertical accuracy by only 29 mm (1.1 in).[8][20]
Skycrane "Olga" lifting antenna segment
In August 1974, construction of the main level commenced. Using 45 hydraulic jacks attached to cables strung from a temporary steel crown anchored to the top of the tower, twelve giant steel and wooden bracket forms were slowly raised, ultimately taking about a week to crawl up to their final position. These forms were used to create the brackets that support the main level, as well as a base for the construction of the main level itself. The Top was built of concrete poured into a wooden frame attached to rebar at the lower level deck, and then reinforced with a large steel compression band around the outside.[20]
While still under construction, the CN Tower officially became the world's tallest free-standing structure on March 31, 1975.[6]
The antenna was originally to be raised by crane as well, but, during construction, theSikorsky S-64 Skycrane helicopter became available when theUnited States Army sold one to civilian operators. The helicopter, named "Olga", was first used to remove the crane, and then flew the antenna up in 36 sections.
The flights of the antenna pieces were a minor tourist attraction of their own, and the schedule was printed in local newspapers. Use of the helicopter saved months of construction time, with this phase taking only three and a half weeks instead of the planned six months. The tower was topped-off on April 2, 1975, after 26 months of construction, officially capturing the height record fromMoscow'sOstankino Tower, and bringing the total mass to 118,000 t (130,000 short tons; 116,000 long tons).
Two years into the construction, plans for Metro Centre were scrapped, leaving the tower isolated on the Railway Lands in what was then a largely abandoned light-industrial space. This caused serious problems for tourists to access the tower. Ned Baldwin, project architect with John Andrews, wrote at the time that "All of the logic which dictated the design of the lower accommodation has been upset," and that "Under such ludicrous circumstances Canadian National would hardly have chosen this location to build."[21]
Phases of construction
Constructing the base, July 1973
Brackets being raised, August 1974
Helicopter lifting part of antenna, March 1975
Main pod construction, April 1975
Nearing completion, December 1975
Two months after opening, August 1976
Opening
The CN Tower opened on June 26, 1976.[22] The construction costs of approximatelyCA$63 million ($318 million in 2023 dollars)[23] were repaid in fifteen years.[24]
From the mid-1970s to the mid-1980s, the CN Tower was practically the only development along Front Street West; it was still possible to see Lake Ontario from the foot of the CN Tower due to the expansive parking lots and lack of development in the area at the time. As the area around the tower was developed, particularly with the completion of theMetro Toronto Convention Centre (north building) in 1984 and SkyDome in 1989 (renamedRogers Centre in 2005), the former Railway Lands were redeveloped and the tower became the centre of a newly developing entertainment area. Access was greatly improved with the construction of theSkyWalk in 1989, which connected the tower and SkyDome to the nearbyUnion Station railway andsubway station, and, in turn, to the city'sPath underground pedestrian system. By the mid-1990s, it was the centre of a thriving tourist district. The entire area continues to be an area of intense building, notably aboom incondominium construction inthe early 21st century, as well as the 2013 opening of theRipley's Aquarium by the base of the tower.[5][8][20]
Early years
When the CN Tower opened in 1976, there were three public observation points: The Top (then known as the Space Deck) that stands at 447 m (1,467 ft), the Indoor Observation Level (later named Main Observation Level) at 346 m (1,135 ft), and the Outdoor Observation Terrace (at the same level as the Glass Floor) at 342 m (1,122 ft).[5][20] One floor above the Indoor Observation Level was the Top of Toronto Restaurant (now named "360 The Restaurant at the CN Tower"), which completed a revolution once every 72 minutes.[25]
The tower would garner worldwide media attention when stuntmanDar Robinson jumped off the CN Tower on two occasions in 1979 and 1980. The first was for a scene from the movieHighpoint, in which Robinson receivedCA$250,000 ($981,875 in 2023 dollars)[23] for the stunt. The second was for a personaldocumentary. The first stunt had him use a parachute that he deployed three seconds before impact with the ground, while the second one used a wire decelerator attached to his back.[26]
On June 26, 1986, the tenth anniversary of the tower's opening,high-rise firefighting and rescue advocateDan Goodwin, in a sponsored publicity event, used his hands and feet to climb the outside of the tower, a feat he performed twice on the same day. Following both ascents, he used multiple rappels to descend to the ground.[27]
From 1985 to 1992, the CN Tower basement level hosted the world's first flightsimulator ride,Tour of the Universe, based on the flight of aSpace Shuttle. The ride was replaced in 1992 with a similar attraction entitled "Space Race." It was later dismantled and replaced by two other rides in 1998 and 1999.
A glass floor at an elevation of 342 m (1,122 ft) was installed in 1994.[20] Canadian National Railway sold the tower to Canada Lands Company prior to privatizing the company in 1995, when it divested all operations not directly related to its core freight shipping businesses. The tower's name and wordmark were adjusted to remove the CN railways logo, and the tower's official name was renamed Canada's National Tower (from Canadian National Tower),[28] though the tower is commonly called the CN Tower.
Further changes were made from 1997 to January 2004:TrizecHahn Corporation managed the tower and instituted several expansion projects including aCA$26 million entertainment expansion, the 1997 addition of two new elevators (to a total of six) and the consequential relocation of the staircase from the north side leg to inside the core of the building, a conversion that also added nine stairs to the climb. TrizecHahn also owned theWillis Tower (Sears Tower at the time) in Chicago approximately at the same time.
In 2007,light-emitting diode (LED) lights replaced the incandescent lights that lit the CN Tower at night. This was done to take advantage of the cost savings of LED lights over incandescent lights. The colour of the LED lights can change, compared to the constant white colour of the incandescent lights. On September 12, 2007,Burj Khalifa in Dubai, then under construction and known as Burj Dubai, surpassed the CN Tower as the world's tallest free-standing structure on land.[29] In 2008, glass panels were installed in one of the CN Tower elevators, which established a world record (346 m (1,135 ft)) for highest glass floor panelled elevator in the world.
2010s: EdgeWalk
EdgeWalk atop the main pod
On August 1, 2011, the CN Tower opened the EdgeWalk, an amusement in which thrill-seekers can walk on and around the roof of the main pod of the tower at 356 m (1,168.0 ft), which is directly above the 360 Restaurant.[30] It is the world's highest full-circle, hands-free walk. Visitors are tethered to an overhead rail system and walk around the edge of the CN Tower's main pod above the 360 Restaurant on a 1.5-metre (4.9 ft) metal floor.[31] The attraction is closed throughout the winter and during periods of electrical storms and high winds.
The tower and surrounding areas were prominent in the2015 Pan American Games production. Inthe opening ceremony, a pre-recorded segment featured track-and-field athleteBruny Surin passing the flame to sprinterDonovan Bailey on the EdgeWalk and parachuting into Rogers Centre. A fireworks display off the tower concluded both the opening and closing ceremonies.
Canada 150
On July 1, 2017, as part of the nationwide celebrations forCanada 150, which celebrated the 150th anniversary ofCanadian Confederation, fireworks were once again shot from the tower in a five-minute display coordinated with the tower lights and music broadcast on a local radio station.
2020s
The CN Tower closed during much of theCOVID-19 pandemic. During much of the pandemic, the gift shop was renovated to take advantage of the lack of visitors from the tower's closure.
The CN Tower was closed during theG20 summit on June 26–27, 2010, for security reasons, given its proximity to the Metro Toronto Convention Centre and ongoingcitywide protests and riots.
The CN Tower was closed from 2020 to 2021 due toCOVID-19 pandemic restrictions throughout Ontario.
The CN Tower was closed on December 16, 2021, due to glass falling off from heavy winds.[33]
Structure
Elevator going upView from 360 RestaurantView straight down from the SkyPod to the roof of the Observation Level
The CN Tower consists of several substructures. The main portion of the tower is a hollow concrete hexagonal pillar containing thestairwells and power and plumbing connections. The tower's sixelevators are located in the three inverted angles created by the Tower's hexagonal shape (two elevators per angle). Each of the three elevator shafts is lined with glass, allowing for views of the city as the glass-windowed elevators make their way through the tower. The stairwell was originally located in one of these angles (the one facing north), but was moved into the central hollow of the tower; the tower's new fifth and sixth elevators were placed in the hexagonal angle that once contained the stairwell. On top of the main concrete portion of the tower is a 102 m (334.6 ft) tall metal broadcast antenna, carrying television and radio signals. There are three visitor areas:[34]
the Lower Observation Level, located at an elevation of 342 m (1,122 ft). It contains the Glass Floor and Outdoor Terrace.
the Main Observation Level, at 346 m (1,135 ft). It was formerly known as "Indoor Lookout Level" and "Indoor Observation Level".
The Top, at 446.5 m (1,465 ft), just below the metalantenna. It was formerly known as "SkyPod" and "Space Deck".
The hexagonal shape is visible between the two highest areas; however, below the main deck, three large supporting legs give the tower the appearance of a largetripod.
The main deck level has seven storeys, some of which are open to the public. Below the public areas—at 338 m (1,108.9 ft)—is a large white donut-shapedradome containing the structure'sUHF transmitters. The glass floor at the Lower Observation Level has an area of 24 m2 (258 sq ft) and can withstand a pressure of 4.1megapascals (595 psi). The floor's thermal glass units are 64 mm (2.5 in) thick, consisting of a pane of 25 mm (1.0 in) laminated glass, 25 mm (1.0 in) airspace and a pane of 13 mm (0.5 in) laminated glass. In 2008, one elevator was upgraded to add a glass floor panel, believed to have the highest vertical rise of any elevator equipped with this feature.[35] The Horizons Cafe and the lookout level are at 346 m (1,135.2 ft). The 360 Restaurant (formally "360 The Restaurant at the CN Tower"), arevolving restaurant that completes a full rotation once every 72 minutes, is at 351 m (1,151.6 ft). When the tower first opened, it also featured a discotheque named Sparkles (at the Indoor Observation Level), billed as the highest disco and dance floor in the world.[36]
A metal staircase reaches the main deck level after 1,776 steps,[5][38] and The Top 100 m (328 ft) above after 2,579 steps; it is the tallest metal staircase on Earth. These stairs are intended for emergency use only except for charity stair-climb events two times during the year.[39][40] The average climber takes approximately 30 minutes to climb to the base of the radome, but the fastest climb on record is 7 minutes and 52 seconds in 1989 by Brendan Keenoy, anOntario Provincial Police officer.[40] In 2002, Canadian Olympian andParalympic championJeff Adams climbed the stairs of the tower in a specially designedwheelchair. The stairs were originally on one of the three sides of the tower (facing north), with a glass view, but these were later replaced with the third elevator pair and the stairs were moved to the inside of the core.[38] Top climbs on the new, windowless stairwell used since around 2003 have generally been over ten minutes.[41]
Afreezing rain storm on March 2, 2007, resulted in a layer of ice several centimetres thick forming on the side of the tower and other downtown buildings. The sun thawed the ice, then winds of up to 90 km/h (56 mph) blew some of it away from the structure. There were fears that cars and windows of nearby buildings would be smashed by large chunks of ice. In response, police closed some streets surrounding the tower. During morning rush hour on March 5 of the same year, police expanded the area of closed streets to include theGardiner Expressway 310 m (1,017 ft) away from the tower as increased winds blew the ice farther, as far north asKing Street West, 490 m (1,608 ft) away, where ataxicab window was shattered. Subsequently, on March 6, 2007, the Gardiner Expressway reopened after winds abated.[42]
On April 16, 2018, falling ice from the CN Tower punctured the roof of the nearbyRogers Centre stadium, causing theToronto Blue Jays to postpone the game that day to the following day as adoubleheader; this was the third doubleheader held at the Rogers Centre. On April 20 of the same year, the CN Tower reopened.[43]
Safety features
In August 2000, a fire broke out at theOstankino Tower in Moscow, killing three people and causing extensive damage. The fire was blamed on poor maintenance and outdated equipment. The failure of the fire-suppression systems and the lack of proper equipment for firefighters allowed the fire to destroy most of the interior and sparked fears the tower might even collapse.
The Ostankino Tower was completed nine years before the CN Tower and is only 13 m (43 ft) shorter.[44] The parallels between the towers led to some concern that the CN Tower could be at risk of a similar tragedy. However, Canadian officials subsequently stated that it is "highly unlikely" that a similar disaster could occur at the CN Tower, as it has important safeguards that were not present in the Ostankino Tower. Specifically, officials cited:
the fireproof building materials used in the tower's construction,
frequent and stringent safety inspections,
an extensive sprinkler system,
a 24-hour emergency monitoring operation,
two 68,160-litre (15,000-imperial gallon; 18,006-US gallon) water reservoirs at the top, which are automatically replenished,
a fire hose at the base of the structure capable of sending 2,725 L/min (720 U.S. gal/min; 599 imp gal/min) to any location in the tower,
a ban on natural gas appliances anywhere in the tower (including the restaurant in the main pod),
an elevator that can be used during a fire as it runs up the outside of the building and can be powered by three emergency generators at the base of the structure (unlike the elevator at the Ostankino Tower, which malfunctioned).[45]
Officials also noted that the CN Tower has an excellent safety record, although there was an electrical fire in the antennas on August 16, 2017 — the tower's first fire.[45][46][47][48] Moreover, other supertall structures built between 1967 and 1976 — such as theWillis Tower (formerly the Sears Tower), theWorld Trade Center (until itsdestruction on September 11, 2001), theFernsehturm Berlin, theAon Center, 875 North Michigan Avenue (formerly theJohn Hancock Center), and First Canadian Place — also have excellent safety records, which suggests that the Ostankino Tower accident was a rare safety failure, and that the likelihood of similar events occurring at other supertall structures is extremely low.
The CN Tower was originally lit at night withincandescent lights, which were removed in 1997 because they were inefficient and expensive to repair. In June 2007, the tower was outfitted with 1,330 super-bright LED lights inside the elevator shafts, shooting over the main pod and upward to the top of the tower's mast to light the tower from dusk until 2 a.m. the next calendar day. The official opening ceremony took place on June 28, 2007, before theCanada Day holiday weekend.
Programmed remotely from adesktop computer with awireless network interface controller inBurlington, Ontario, the LEDs use less energy to light than the previous incandescent lights (10% less energy than the dimly lit version and 60% less than the brightly lit version).[52] The estimated cost to use the LEDs is $1,000 per month.
During the spring and autumnbird migration seasons, the lights are turned off to comply with the voluntary Fatal Light Awareness Program, which "encourages buildings to dim unnecessary exterior lighting to mitigate bird mortality during spring and summer migration."[53]
The CN Tower is the tallest freestanding structure in the Western Hemisphere. As of 2013, there were two otherfreestanding structures in the Western Hemisphere exceeding 500 m (1,640.4 ft) in height: the Willis Tower in Chicago, which stands at 527 m (1,729.0 ft) when measured to its pinnacle, andOne World Trade Center in New York City, which has a pinnacle height of 541.33 m (1,776.0 ft), or approximately 12 m (39.4 ft) shorter than the CN Tower. Due to the symbolism of the number 1776 (the year of the signing of theUnited States Declaration of Independence), the height of One World Trade Center is unlikely to be increased. The proposedChicago Spire was expected to exceed the height of the CN Tower, but its construction was halted early due to financial difficulties amid theGreat Recession, and was eventually cancelled in 2010 and replaced with 400 Lake Shore.[54]
Height distinction debate
"World's Tallest Tower" title
Guinness World Records has called the CN Tower "the world's tallest self-supporting tower" and "the world's tallest free-standing tower".[55][56] Although Guinness did list this description of the CN Tower under the heading "tallest building" at least once,[56] it has also listed it under "tallest tower", omitting it from its list of "tallest buildings."[55] In 1996, Guinness changed the tower's classification to "World's Tallest Building and Freestanding Structure".Emporis and theCouncil on Tall Buildings and Urban Habitat both listed the CN Tower as theworld's tallest free-standing structure on land, and specifically state that the CN Tower is not a true building, thereby awarding the title ofworld's tallest building toTaipei 101, which is 44 m (144 ft) shorter than the CN Tower.[14][57] The issue of what was tallest became moot when Burj Khalifa, then under construction, exceeded the height of the CN Tower in 2007 (see below).
Although the CN Tower contains a restaurant, a gift shop and multiple observation levels, it does not have floors continuously from the ground, and thereforeit is not considered a building by the Council on Tall Buildings and Urban Habitat (CTBUH) or Emporis. CTBUH defines a building as "a structure that is designed for residential, business, or manufacturing purposes. An essential characteristic of a building is that it has floors."[57] The CN Tower and other similar structures—such as the Ostankino Tower in Moscow, Russia; theOriental Pearl Tower inShanghai, China;The Strat inLas Vegas, Nevada, United States; and theEiffel Tower inParis, France—are categorized as "towers", which are free-standing structures that may have observation decks and a few other habitable levels, but do not have floors from the ground up. The CN Tower was the tallest tower by this definition until 2010 (see below).[14]
On September 12, 2007, Burj Khalifa, which is a hotel, residential and commercial building inDubai, United Arab Emirates (formerly known as Burj Dubai before opening), passed the CN Tower's 553.33-m[8] height. The CN Tower held the record of the tallest freestanding structure on land for over 30 years.[29]
After Burj Khalifa had been formally recognized by the Guinness World Records as the world's tallest freestanding structure, Guinness re-certified CN Tower as the world's tallest freestanding tower.[58] The tower definition used by Guinness was defined by the Council on Tall Buildings and Urban Habitat as 'a building in which less than 50% of the construction is usable floor space'.Guinness World Records editor-in-chief Craig Glenday announced that Burj Khalifa was not classified as a tower because it has too much usable floor space to be considered to be a tower.[59] CN Tower still held world records for highest above ground wine cellar (in 360 Restaurant) at 351 m, highest above-ground restaurant at 346 m (Horizons Restaurant),[60] and tallest free-standing concrete tower during Guinness's recertification. The CN Tower was surpassed in 2009 by theCanton Tower inGuangzhou, China, which stands at 604 m (1,982 ft) tall, as the world's tallest tower; which in turn was surpassed by theTokyo Skytree in 2011, which currently is the tallest tower at 634.0 m (2,080.1 ft) in height.[12][61] The CN Tower, as of 2022, stands as the tenth-tallest free-standing structure on land, remains the tallest free-standing structure in theWestern Hemisphere, and is the third-tallest tower.[1][62][63] The CN Tower is the second-tallest free-standing structure in theCommonwealth of Nations behindMerdeka 118 inKuala Lumpur,Malaysia.
There is noAM broadcasting from the CN Tower.[65] TheFM transmitters are situated in a 102 m-tall (335 ft) metal broadcast antenna, on top of the main concrete portion of the tower at an elevation above 446.5 m (1,465 ft) from the ground.
Amateur radiorepeaters "2-Tango" (VHF) and "4-Tango" (440/70 cmUHF)—owned and operated by the Toronto FM Communications Society, under callsign VE3TWR[67]
In popular culture
The CN Tower has been featured in numerous films, television shows, music recording covers, and video games. The tower also has its own official mascot, which resembles the tower itself.[68]
Views is a 2016 studio album released on April 29, 2016, by Canadian rapperDrake. The cover artwork features Drake sitting atop the CN Tower in Toronto.[69] Drake appeared significantly larger than life-size on the cover, and the CN Tower'sTwitter account later confirmed it to bephoto-edited.[70]
^"Toronto's Most Extreme Attraction". CN Tower. Archived fromthe original on March 9, 2012. RetrievedFebruary 25, 2012.It is the world's highest full circle hands-free walk on a 5 ft (1.5 metres) wide ledge encircling the top of the tower's main pod, 356m/1168ft (116 storeys) above the ground.
^"FM Query & FM List Results". Federal Communications Commission – Audio Division. April 9, 2008. Archived fromthe original on August 2, 2012. RetrievedApril 9, 2008.
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