CN Tower

Origins and Design Evolution

The CN Tower's inception in 1968 was driven by the practical need of the Canadian National Railway to solve broadcast signal degradation caused by the reflective glass of Toronto's new skyscrapers, such as First Canadian Place. The railway sought a new antenna at least 300 metres tall and envisioned a hub for microwave communications links visible across the city. The project became official in 1972 as a centrepiece of the planned Metro Centre development on the Railway Lands, a large switching yard made redundant after the 1965 opening of the MacMillan Yard north of the city. The original architectural concept, conceived by the team including John Andrews Architects and Webb, Zerafa, Menkes, Housden Architects, was a tripod of three cylindrical pillars linked by bridges. This design evolved significantly into the single continuous hexagonal core seen today, with three support legs forming a Y-shape at ground level. A key late addition was the Space Deck, now called The Top, championed by Bud Andrews of the Metro Centre Developments Group, who argued the higher observation deck would be a major tourist draw. This change, along with other subtle modifications, was made with the explicit goal of making the tower the world's tallest free-standing structure.

Phases of Construction

Construction, led by the Foundation Company of Canada with steel and antenna work by Canron, commenced on February 6, 1973. The first phase involved excavating 56,000 tonnes of earth and shale to a depth of 15 metres to create a foundation comprising 7,000 cubic metres of concrete, 450 tonnes of rebar, and 36 tonnes of steel cable, built to a thickness of 6.7 metres. This foundation work was completed in just four months. The main concrete pillar was then constructed using a hydraulically raised slipform, an innovative metal platform that jacked itself upward about six metres per day as concrete set beneath it. Concrete was poured intermittently until February 22, 1974, at which point the structure surpassed the Inco Superstack to become Canada's tallest. All 40,500 cubic metres of concrete were mixed on-site to ensure consistency, and vertical accuracy was maintained within 29 millimetres using plumb bobs and ground telescopes. Construction of the main pod began in August 1974 using twelve giant steel and wooden bracket forms slowly raised by 45 hydraulic jacks over roughly a week. The antenna, a 102-metre structure, was lifted in 36 sections by a Sikorsky S-64 Skycrane helicopter named Olga in April 1975, a process that took three and a half weeks and saved months of construction time. The tower was topped off on April 2, 1975, achieving its record height with a total mass of 118,000 tonnes.

• Phase 1 (Feb 1973): Foundation excavation and pouring.
• Phase 3 (Aug 1974): Raising of forms for main pod construction.
• Phase 4 (Apr 1975): Helicopter lift of antenna sections.
• Completion: Topped off April 2, 1975. Opened June 26, 1976.

Architectural and Structural Details

The CN Tower's structural form is defined by its hollow concrete hexagonal core, which contains stairwells and utility connections. The six elevators are located in the three inverted angles created by the hexagon's shape, with two elevators per shaft. Each elevator shaft is lined with glass, providing panoramic views during the ascent. The original stairwell was in the north-facing angle but was relocated into the central core during the 1997 expansion, freeing space for two new elevators. The tower is supported by three large legs that blend into the hexagon below the main deck, creating the distinctive tripod appearance at its base. The main pod houses seven storeys, including public and mechanical spaces. At 338 metres, a large white radome contains the structure's UHF transmitters. The Glass Floor on the Lower Observation Level has an area of 24 square metres and is engineered to withstand a pressure of 4.1 megapascals. Its construction involves 64 millimetres of thermal glass: a 25-millimetre pane of laminated glass, a 25-millimetre airspace, and a 13-millimetre pane of laminated glass. The 360 Restaurant revolves on a mechanism that completes a full rotation every 72 minutes. When the tower opened, it also featured a discotheque named Sparkles on the Indoor Observation Level, billed as the world's highest dance floor.

Visitor Attractions and Historical Additions

Upon its 1976 opening, the CN Tower offered three public observation points: The Top at 447 metres, the Indoor Observation Level at 346 metres, and the Outdoor Observation Terrace at 342 metres. The tower's attraction portfolio has been consistently expanded and upgraded. In 1994, the Glass Floor was installed on the Lower Observation Level, becoming an immediate sensation. The 360 Restaurant, originally named the Top of Toronto Restaurant, has operated since opening day. From 1985 to 1992, the basement level hosted Tour of the Universe, the world's first flight simulator ride, which was later replaced by Space Race and other simulator attractions. A major renovation from 1997 to 2004, managed by TrizecHahn Corporation, added two elevators and relocated the internal staircase. In 2007, the exterior lighting system was upgraded from incandescent to programmable LED lights, allowing for dynamic colour displays. The following year, one elevator was fitted with a glass floor panel, creating the elevator with the highest vertical rise featuring such a floor. The most significant new attraction, the EdgeWalk, opened on August 1, 2011. This involves participants walking tethered on a 1.5-metre wide metal floor around the roof of the main pod at 356 metres directly above the restaurant.

Ownership, Management, and Financial History

The tower was conceived, financed, and built by Canadian National Railway as a corporate project. The construction cost of approximately CA$63 million was repaid within fifteen years of its 1976 opening. In 1995, as CN prepared for privatization, it divested all non-core freight assets, transferring ownership of the tower to the Canada Lands Company, a federal Crown corporation. The tower's official name was changed to Canada's National Tower, though the original CN Tower name persisted in common use. From 1997 to January 2004, management was contracted to TrizecHahn Corporation, which also owned Chicago's Willis Tower at the time. TrizecHahn instituted a CA$26 million entertainment expansion, which included the addition of the fifth and sixth elevators and the staircase relocation. This period of private management focused on enhancing the visitor experience and commercial operations. The tower's primary function as a broadcast facility continues, with its antenna transmitting signals across the Toronto region, fulfilling the original communications mandate that justified its construction.

Cultural Impact and Notable Events

The CN Tower quickly became a global symbol of Toronto and Canadian engineering prowess. It was declared one of the modern Seven Wonders of the World by the American Society of Civil Engineers in 1995 and is a member of the World Federation of Great Towers. The tower has been the stage for numerous stunts and media events. Stuntman Dar Robinson performed two parachute jumps from the tower in 1979 and 1980, the first for the film Highpoint for which he was paid CA$250,000. On the tower's tenth anniversary in 1986, climber Dan Goodwin scaled its exterior twice in one day using his hands and feet, descending by rappel. The tower played a prominent role in the 2015 Pan American Games, with a pre-recorded segment featuring athletes on the EdgeWalk and a parachute jump into Rogers Centre, and fireworks launched from its structure. For Canada's 150th anniversary in 2017, a five-minute fireworks display coordinated with tower lights and music was held. The EdgeWalk was featured on national television in 2013 when Canadian comedian Rick Mercer and singer Jann Arden experienced it for an episode of the Rick Mercer Report. The tower's isolation in its early years, due to the cancellation of the Metro Centre plan, was a significant challenge, but the area later developed into a thriving tourist district with the addition of the Metro Toronto Convention Centre, Rogers Centre, and Ripley's Aquarium.

Record-Holding History and Statistics

The pursuit of height records was integral to the CN Tower's design and construction. It officially became the world's tallest free-standing structure on March 31, 1975, while still under construction, surpassing Moscow's Ostankino Tower. It held this title for 32 years until the Burj Khalifa in Dubai surpassed it on September 12, 2007. The tower was also the world's tallest tower until the Canton Tower claimed the title in 2009. The Top observation deck was the highest public observation deck in the world until the Shanghai World Financial Center opened in 2008. The EdgeWalk, opened in 2011, holds the current record for the world's highest full-circle, hands-free walk. The glass-floored elevator installed in 2008 set a record for the highest vertical rise for an elevator with a glass floor panel. In terms of construction statistics, the tower used 40,500 cubic metres of concrete, contains a 102-metre antenna, and has a total mass of 118,000 tonnes. The main staircase has 1,776 steps to the main deck and 2,579 steps to The Top.

• Tallest free-standing structure: Record held from March 31, 1975, to September 12, 2007.
• Tallest tower: Record held from 1976 to 2009.
• Highest observation deck (The Top): Record held from 1976 to 2008.
• Highest hands-free walk (EdgeWalk): Current record holder since 2011.
• Concrete volume: 40,500 m³ used in construction.
• Total mass: 118,000 tonnes upon completion.

Temporary Closures and Operational History

The CN Tower has closed its doors to the public on several notable occasions, each reflecting broader events. It was closed on September 11, 2001, in the immediate aftermath of the terrorist attacks in the United States. For security reasons related to the G20 summit held in Toronto and its proximity to the Metro Toronto Convention Centre, the tower was closed on June 26 and 27, 2010, a period marked by citywide protests. The most prolonged closure occurred from 2020 into 2021 due to public health restrictions implemented across Ontario during the COVID-19 pandemic. This closure period was used to renovate the gift shop. A brief, safety-related closure happened on December 16, 2021, after heavy winds caused glass to fall from the structure. Operationally, the EdgeWalk attraction is closed throughout the winter and during periods of electrical storms and high winds. The tower's early years were marked by access difficulties due to the lack of surrounding development, a problem later solved by the construction of the SkyWalk pedestrian link to Union Station in 1989 and the general redevelopment of the Railway Lands.

Questions about CN Tower

How tall is the CN Tower and what records did it hold?

The CN Tower stands 553.3 metres tall. It held the record as the world's tallest free-standing structure for 32 years, from 1975 until 2007 when the Burj Khalifa surpassed it. It was also the world's tallest tower until 2009. It remains the tallest free-standing structure in North America and the Western Hemisphere. The EdgeWalk attraction holds the current record for the world's highest full-circle, hands-free walk.

When did the CN Tower open and how much did it cost to build?

The CN Tower opened to the public on June 26, 1976. The total construction cost was approximately CA$63 million, which equates to about $333 million in 2025 dollars. The project took 26 months of active construction, beginning on February 6, 1973, and was topped off with the antenna installation in April 1975. The cost was repaid within fifteen years of opening.

What are the main attractions inside the CN Tower?

The tower features multiple observation decks: The Top at 446.5 metres, the Main Observation Level at 346 metres, and the Lower Observation Level at 342 metres which includes the Glass Floor. The 360 Restaurant, a revolving dining venue, is located at 351 metres. The EdgeWalk, opened in 2011, is a thrill attraction where tethered participants walk around the main pod's roof at 356 metres. The facility also houses gift shops, cafes, and historically featured simulator rides like Tour of the Universe.

Who owns the CN Tower?

The CN Tower is owned by Canada Lands Company, a federal Crown corporation. It was originally built and owned by Canadian National Railway. Prior to CN's privatization in 1995, the railway transferred the tower to Canada Lands as part of divesting non-core assets. The tower's official name was subsequently adjusted to Canada's National Tower, though it is universally known as the CN Tower.

Has the CN Tower ever been closed for extended periods?

Yes, the tower has experienced several extended closures. It was closed following the September 11, 2001 attacks, during the G20 summit in June 2010, and for most of 2020 and into 2021 due to COVID-19 pandemic restrictions in Ontario. It also closed briefly in December 2021 after high winds caused glass to detach. The EdgeWalk attraction closes seasonally each winter.

What was the EdgeWalk and when did it open?

The EdgeWalk is an outdoor thrill attraction where participants, secured by an overhead tether system, walk hands-free around the edge of the CN Tower's main pod at a height of 356 metres. It opened on August 1, 2011, and is marketed as the world's highest full-circle walk of its kind. The attraction is closed during winter and in adverse weather conditions like electrical storms or high winds. It was featured on the Rick Mercer Report in 2013.

Sources and further reading

• CN Tower (Wikipedia)
• CN Tower (cntower.ca)
• CN Tower in Toronto | Restaurants, Attractions & Activities (destinationtoronto.com)
• CN Tower, Toronto, Ontario, Canada, Landmark Review (cntraveler.com)

Checked by the Your Space Hamilton desk. Last updated 2026-10-18.