CN Tower

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The CN Tower is the tallest free-standing structure on land in the world, at 553.33 metres (1,815 ft., 5 inches). It is located in the city of Toronto, Ontario, and is considered the signature icon of the city (Geographic coordinates: Template:Coor dms). The CN Tower attracts over two million visitors annually.

CN is the official acronym of the Canadian National Railway, but following the railway's decision to divest non-core freight railway assets during the lead-up to the company's privatization in 1995, the CN Tower was transferred to the Canada Lands Company (CLC), a federal Crown corporation responsible for real estate development. Since the citizens of Toronto wished to retain the name CN Tower, the acronym CN now officially stands for Canada's National rather than the original Canadian National.

1 Structure
2 History
3 Size comparisons
4 Trivia
5 See also
6 External links

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Structure

The Sky Pod, a small enclosed platform elevated high above the main observation floor, is located at 447 m (1,465 feet), and is the highest public observation deck in the world. From its top, it's possible on a clear day to see approximately 100-120km away and even see an outline of the city of Rochester across Lake Ontario in the United States.

A metal staircase with 1,776 steps reaches the Sky Pod level (447m/1465ft/147 stories) and is the tallest metal staircase on earth. These stairs are intended for emergency use and are not open to the public, except for twice a year for charity stairclimb events: around Earth Day in the spring by the World Wildlife Fund; and in the fall by the United Way's Toronto chapter. The average climber takes approximately 30 minutes to climb to the base of the radome (the white ring around the bottom of the main pod), but the fastest climb on record is 5 minutes and 52 seconds by a Toronto city firefighter.

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At 342 m (1,122 feet) is the Glass Floor and Outdoor Observation Deck, the Glass Floor is 23.8 square metres (256 square ft.) and can withstand the weight of 4,137 kPa (600 pounds per square inch) or 14 large hippopotami.

At 346 m (1,136 feet) is the Horizons Cafe and the Indoor Observation Deck, and at 351 m (1,150 feet) is the 360 Restaurant, which rotates once every 72 minutes. The restaurant has a minimum purchase requirement and the highest wine cellar in the world offering a vast wine selection.

The structure's microwave receivers for distant signals are housed at 338 metres, and the top of the transmission antenna is at the apex of the tower.

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History

Construction on the CN Tower started on February 6, 1973 by Canadian National Railway who wanted to build a large TV and radio communication platform to service the Greater Toronto Area and also to demonstrate the strength of Canadian industry. 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). The project proceeded 24 hours a day, five days a week for 40 months with 1,537 workers involved in the project, finally opening to the public on June 26, 1976. The construction costs of approximately $330 million 2005 Canadian Dollars (approximately $260 million 2005 U.S. Dollars) were repaid in fifteen years.

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From 1997 to January 2004, TrizecHahn Corporation managed the building and instituted several expansion projects including a $26 million entertainment expansion and revitalization that included the addition of two new elevators (to a total of six) and the relocation of the staircase from the cityside (north side) shaft to inside the core of the building.

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Size comparisons

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. The following year, the Guinness Book of World Records officially changed the CN Tower's classification to "World's Tallest Building and Free-Standing Structure" and it retains that title to this day.

There are also many guyed towers taller than the CN Tower, the current tallest being the KVLY-TV tower in North Dakota at 628 m (2,063 feet) tall (see List of masts), but these are guy-wire supported structures and not classified as free-standing. The Petronius Compliant Tower (an oil platform) at 645 m (2,116 feet), is a taller free-standing structure, however all but its top is under water. If built, a 1,000 m tower for a solarthermic power station in Australia will break the record. The Burj Dubai, slated for completion in 2008, would according to present claims by its developers, also become a taller free-standing land structure than CN Tower. Now Chicago city council's planning commission has given its blessing to the Fordham Spire, a 610-metre corkscrewing colossus to be completed by 2010. See World's tallest structures for further analysis of the tallest man-made structures.

The builders of the CN Tower did not expect that it would hold the tallest structure record for thirty years. Previous record holders had quickly been supplanted. Several rivals have been proposed and most schemes collapsed. This is a part because of the development of cable television soon after the tower was built which greatly reduced the need for such broadcasting centres, especially in urban areas. Only in cities are there enough tourists to make such a tower viable as a tourist attraction.

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Trivia

The CN Tower is 13 metres taller than Moscow's Ostankino Tower.
The CN Tower is struck by lightning over 78 times a year.
The CN Tower has a wind tolerance level of 420km/h (260 mph).
The elevators go at over 22km/h (15 mph) taking 58 seconds to 61 seconds to reach the Lookout (indoor observation deck) and 360 restaurant levels respectively.
The CN Tower is almost twice as tall as the Eiffel Tower.
It is the tallest member of the World Federation of Great Towers.
The Glass Floor can withstand a weight of 600lbs per sq inch (109 kg per sq cm) or the equivalent to 14 adult hippopotami.
In winds of 120mph the tower sways 1.07 m (3 1/2 ft) from centre at the Antenna, 0.46 m (1 1/2 ft) from centre at the SkyPod, and 22.9 cm (9 inches) from centre at the Main Pod.
A Sikorsky skycrane helicopter nicknamed 'Olga' was used to lower the communications antenna into place on the tower.
The CN Tower is able to withstand an earthquake of 8.5 on the Richter Scale.
In 1979, Norman Alexander and Joe Squire hauled a 440 lb. piano up the stairs in 7 1/2 hours.
On July 23, 1999 Ashrita Furman became the fastest person to go up the CN Tower using a Pogo stick.
In 2001, a group of environmentalists illegally scaled the tower to place a banner protesting the policies of United States President George W. Bush on the tower.
The tower is the only landmark from Canada that appears in the city-building/simulation computer games SimCity 3000 and SimCity 4.
The amount of cement used in the CN Tower is enough to build a sidewalk from Toronto to Kingston (about 250 km away)
The tower is sometimes mistaken by some for the Seattle Space Needle due to their similar appearances; during an appearance by American talk show host Conan O'Brien to Toronto, he staged a mock fight between two men costumed up as the respective towers on his show.