The World's Tallest Freestanding Towers
7 Kuala Lumpur Tower: 421 meters, Kuala Lumpur, Malaysia. This tower is a fluted concrete spire. The foundation was done as a continuous concrete pour of 50,000 cubic meters, lasting 31 hours, a record for Malaysia. Its head contains 11 floors, which hold an observation deck, revolving restaurant, broadcasting facilities and building services. The main lobby features glass domes arranged in the shape of muqarnas (types of corbels found in traditional Islamic architecture). The tower acts as an Islamic observatory for people to observe the crescent moon marking the beginning of three major holidays: Ramadan, Eid al-Fitr and Eid al-Adha. It was designed by Kumpulan Senireka Sdn. Bhd. Construction was handled by a German contractor, Wayss & Freytag, and it was completed in 1995. Although the nearby twin Petronas Towers (452 meters), located only one mile away, are taller structures, the Kualo Lumpur ower is higher because it stands on a small hill.
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2 Canton Tower: 600 meters (1,969 ft), Guangzhou, China. A cylinder gracefully tapering to a waist, the tower was briefly the world's tallest before being surpassed by the Tokyo Skytree. A lattice of spiraling, 3.7-m-dia steel columns joined by rings and braces surrounds a central concrete column. It is topped by a broadcast transmission tower. Design team members from Information Based Architecture of the Netherlands, in collaboration with structural engineers from Arup, used parametric associative software to refine the geometry. The section between 80 m and 170 m contains a 4D cinema, restaurants and outdoor gardens. An open-air staircase wraps around the central column from 170 m to 370 m. There is an outdoor observatory on the rooftop at 488 m, and sixteen observation cars circle the roof edge on a track. The base of the tower contains subway and bus stations, a parking garage, a food court and elevator entrances. Opening in 2010 in time for the Asian Games, the two primary contractors were Guangzhou Municipal Construction Group Ltd. Co. and Shanghai Construction Group.
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9 China Central Television Tower: 405 meters, Beijing, China. A reinforced concrete tower located in Beijing's Haidian district, its turret at 238 meters contains an observatory and a rotating restaurant. Designed by the Design Institute of the Ministry of Radio, Film and Television and completed in 1992, the tower also has an aquarium at its base.
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10 Zhongyuan Tower: 388 meters, Zhengzhou, China. An unusually shaped tower, this structure consists of a central core column surrounded by curving tubular steel columns and rising to a colorfully-striated head structure. It has a revolving restaurant and an observation deck containing the world's largest panoramic painting (3,012 square meters). Built by China State Construction Engineering Corp., the tower was completed in 2011 and designed by Renle Ma and the Ministry of Radio Film and Television Institute of Design. Zhengzhou is a manufacturing and textile center 400 miles south of Beijing.
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3 CN Tower: 553.3�meters (1,815�ft), Toronto, Canada. A hollow, dart-shaped tower of concrete, it was the world's tallest freestanding structure from 1976 to 2007, and it remains the tallest structure in the Western Hemisphere. Economics dictated post-tensioning and slipforming the concrete structure. Post-tensioning saved 25% in construction costs compared to conventional reinforced concrete construction by reducing wall thicknesses and bracing in the structure and reducing the size of the foundation. Three flying buttress-like legs or wings positioned around a hollow hexagonal core make up the heart of the structural system. The tower is anchored by four 30-in dia caissons drilled through 30 ft of earth overburden and as much as 90 ft into shale and one caisson drilled to 350 ft. There also is a 22-ft-thick concrete base weighing 61,729 tons. At the tower's base the wings are 90 ft long and 23 ft wide. The foundation block is reinforced by 48 1/2-in.-dia post-tensioned cables. Two elevator shafts and one stair shaft are situated between the tower's legs. During construction, the Foundation Co. of Canada Ltd. built a Y-shaped, four-level slipform that was raised by 60, 22-ton hydraulic jacks. Concrete was poured continuously by a workforce of 1,532 people. The tower contains 150 post-tensioning cables terminating at six different levels. The seven-story SkyPod at 447 m contains indoor and outdoor observation areas and a revolving restaurant. Developed by Canadian National Railways on a former rail yard, the area has since become an entertainment district. Completed in 1976 at a cost of $63 million U.S., the tower was designed by John Andrews and Webb, Zerafa, Menkes, Housden, both of Toronto. Nicolet, Carrier, Dressel & Associates Ltd., Montreal, was the structural engineer.
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4 Ostankino Tower: 540.1 meters, Moscow, Russia. A tapering concrete column, topped by an antenna, the tower was the tallest freestanding structure in the world from 1967 until the CN Tower passed it in 1976. It remains the tallest such structure in Europe. Formally called the All-Union Television Center, it was built to mark the 50th anniversary of the Russian Revolution. It rests on two foundations. One is a 100-ft-dia concrete pad, extending 66 ft into the ground. From the pad rises a 170-ft high circular prestressed concrete pedestal. From the top of this cylindrical pedestal, 10 prestressed concrete legs extend into the ground to form a second stabilizing foundation. Hydraulic jacks on the ground exert 9,900 tons of force on a total of 4,000 prestressing cables strung along the tower's inner walls. The pedestal is 196 ft in dia at the base, tapering to 26.5 ft at the top. The walls are 19.5 in. thick at the base and 11.7 in. at the top. The tower was built using a 350-ton self-climbing platform that carried a 5-ton crane and two elevators for workers and concrete. It has a circular observation platform at 337 m. In 2000, a fire caused by a short circuit at the 400 m level killed three firefighters and one tower employee after the elevator they were using to carry emergency equipment jammed. The fire spread downward, burning through asbestos walls and also upward, damaging the antenna, causing it to tilt slightly. Elevator service was restored in 2005, and the observatory reopened in 2011. The tower was designed by V.I. Nikitin and cost $100 million to build.
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6 Milad Tower: 435 meters, Tehran, Iran. A graceful spire of reinforced concrete, it has interlacing trusses surrounding the base. The large, conical head structure contains an observation deck and revolving restaurant and is topped by a 120 meter antenna mast. It is part of the International Trade and Convention Centre, along with a hotel, exhibition space, broadcasting studios and food courts. Designed by Mohammad Reza Hafezi, the structure was built by the Boland Payeh Co., and it was completed in 2007.
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1 Tokyo Skytree: 634 meters (2,080 ft), Japan. A structural steel needle, the Skytree is the world's tallest unsupported structure and the second tallest structure of any kind, behind the Burj Khalifa. Its steel trusses surround a central concrete column. There are observatories at 350 m and 450 m as well as a restaurant at 350 m. Japanese broadcasters were motivated to build the Skytree because the 333-meter-tall Tokyo Tower was no longer effective at transmitting, given the emergence of many high-rise buildings which blocked signals. Tobu Railway led the development team, which included six broadcasters. Designed by Nikken Sekkei and built by Obayashi Corp. Construction, work was completed in February 2012 at a cost of $806 million. A large mall at the base of the tower serves the millions of tourists drawn to the tower each year.
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5 Oriental Pearl Tower: 469 meters, Shanghai, China. A striking, colorful landmark, the tower dominates the skyline of Shanghai's Pudong district, flanking the Huangpu River. Two huge spheres, 50 m and 45 m in diameter, contain observatories and restaurants. The base consists of three 9-m-dia vertical stanchions and three 7-m-dia slanting columns. Three vertical columns connect the two spheres, which are 90 m and 267 m above ground. Five small spheres nestled between the central columns between the two large spheres contain 20 hotel rooms. It was the tallest structure in China from its completion in 1994 until 2007, when it was surpassed by the Shanghai World Financial Center. The tower was designed by Shanghai Modern Architectural Design Co. Ltd., and cost $100 million. The tower attracts three million visitors per year.
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8 Tianjin Radio and Television Tower: 415 meters, Tianjin, China. A tapering spire of reinforced concrete, the tower is situated in the middle of a 51-acre lake. The seven-story tower head structure sits at an elevation of 248 meters and contains an observatory and revolving restaurant. Completed in 1991 at a cost of $45 million, the tower offers views of Tianjin, a major port and manufacturing hub in northeast China, and the Bohai Gulf, an arm of the East China Sea.
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The essential function of all tall towers is to enable broadcasters to transmit line-of-sight signals to their customers.
"Broadcasting is a big stick industry, where one tower can cover a whole market," according to Kelly Williams, senior director of Engineering for the National Association of Broadcasters. "You put up a tower to facilitate broadcasting wirelessly."
Towers host a wide variety of antennae, which transmit over the air (analog) television signals, AM and FM radio, telco long lines (which transmit data), pager signals and emergency service channels (including two-way radio).
But tower owners have long realized that their structures have tourism potential. In addition to running observation decks, almost all major towers have restaurants, most of which revolve slowly to offer patrons effortless panoramic views.
Jack Robinson, chief operating officer of CN Tower in Toronto, the tallest freestanding tower in the Western Hemisphere, outlines owners' changing business model:
"We started off in 1976 as a broadcast tower, that was our core business. We have since morphed into a fabulous entertainment complex, with the observation gallery, three restaurants and Edgewalk, which allows thrill seekers to walk along the edge while attached to a harness. Our 360 Restaurant is probably the number one restaurant for marriage proposals in Canada."
CN Tower was built by Canadian National Railway, which was government owned. Since 1995 the structure has been owned by Canada Lands Co., a federal crown corporation operating under the Ministry of Public Works. An expansion in 1998 added a 3D cinema and shopping arcade at the base. The tower is operated for profit, but does not break out figures, and consistently draws 1.5 million customers a year.
"Revenues are up four or five percent every year. We've gone from pretty much a broadcast tower to a vertical theme park," says Robinson.
The U.S. does not make the cut among the 10tallest towers featured in the accompanying slide show. The tallest freestanding tower in the U.S. is the Stratosphere, a 350-meter-tall tower attached to a casino in Las Vegas. It is the 17th-tallest freestanding tower in the world.
