and anchored by twelve steel-and-timber brackets that were slowly pushed up the tower by forty-five hydraulic jacks. The concrete-walled SkyPod, reached by four high-speed, glass-fronted elevators, houses a 400-seat revolving restaurant, a nightclub, and indoor and outdoor observation decks. Later, a 2.5-inch-thick (6.4-centimeter) glass floor was installed. Beneath the SkyPod, delicate microwave dishes and other broadcasting equipment are protected by an annular radome. The concrete tower continues to the Space Deck at 1,465 feet (447 meters)—an observation gallery that on a clear day provides a view with 100-mile (160-kilometer) visibility. A Sikorsky Skycrane helicopter lifted the tower’s 335-foot (100-meter) communications mast in forty sections, each of about 7 tons (6.4 tonnes), and they were bolted together in place. The mast, erected in three weeks, was covered by fiberglass-reinforced sheathing. The maximum sway experienced at the very top in 120-mph (190-kph) winds with 200-mph (320-kph) gusts is 3.5 feet (1.07 meters).

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CN (Canadian National) Tower, Toronto, Canada. John Andrews and Webb Zerafa Menkes Housden Architects; Roger R. Nicolet, structural engineer, 1972–1975. View from Lake Ontario.

The CN Tower was completed in June 1975 and officially opened on 1 October. It cost Can$57 million and took about 1,550 workers forty months to construct. It is nearly twice the height of the Eiffel Tower and more than three times as tall as the Washington Monument. Soaring above Toronto, it is struck by lightning about seventy-five times every year.

In 1995 Canada National passed ownership to a public company, the Canada Lands Company. In June 1998, the CN Tower officially opened a 75,000-square-foot (7,100-square-meter) expansion including an entertainment center, shopping facilities, and restaurants.

Further reading

Campi, Mario. 2000. Skyscrapers: An Architectural Type of Modern Urbansm, Boston: Birkhäuser.

McDermott, Barb, and Gail McKeown. 1999. The CN Tower. Edmonton, Canada: Reidmore Books.

Colosseum (Flavian Amphitheater)

Rome

The Flavian Amphitheater, now in ruins, towers over the southeast end of the Roman Forum, between the Esquiline and Palatine Hills. Its popular name, the Colosseum, was derived from the nearby colossal (120-foot-high, or 37.2-meter) bronze statue of Nero, long since vanished. The most ambitious example of a new building type associated with urbanization, the Colosseum was an architectural feat, even by Roman standards. Its size is awesome, but the logistics of moving crowds to and from their seats was also a major achievement.

The earliest amphitheater on the site was built in timber for the pontifex maximus Gaius Scribonius