The CN Tower at 553.33 meters (1,815 ft., 5 inches) was once the tallest building, tower, and freestanding structure, but as of 2010 retains the title of world's tallest tower.
Construction on the CN Tower began on February 6, 1973 and wrapped up about 40 months later in June 1976. The CN Tower was built at an original cost of $63 million. On April 2, 1975, onlookers gazed up in amazement as a giant Erickson Air-crane Silorsky helicopter placed the final piece of the CN Tower's antenna into place, officially making it the world's tallest building.
The CN Tower was built to withstand an earthquake of 8.5 on the Richter scale (the Kobe earthquake in 1995 was 7.2 on the Richter scale). The upper reaches of the CN Tower were built to withstand winds up to 418 km/h (260 mph). In 1995, the CN Tower is designated a Wonder of the Modern World by the American Society of Civil Engineers.
Lightning strikes the CN Tower an average of 75 times per year. Long copper strips run down the CN Tower to grounding rods buried below ground to prevent damage.
The CN Tower dims unnecessary exterior lights during bird migration seasons to prevent bird injuries. The CN Tower is an incredible 2.79 cm (1.1 inches) within plumb, or, true vertical.
Six glass-faced elevators travel at 22 km/hour (15 miles/hour) to reach the observation deck in 58 seconds. On a clear day, visitors to the CN Tower's observation deck can see over 160 kilometers (100 miles) -- that's all the way to Niagara Falls and across Lake Ontario to New York State. he CN Tower has a hollow 1200' hexagonal core providing stability and flexibility to the full height tower.
The CN Tower's Glass Floor was the first of its kind when it was opened in June 1994. It is 23.8 square meters (256 sq. ft.) of solid glass and 5 times stronger than the required weight-bearing standard for commercial floors. If 14 large hippos could fit in the elevator and get up to the Observation Deck, the Glass Floor could withstand their weight.
The 360 Restaurant makes a complete rotation every 72 minutes giving diners a changing view of Toronto more than 1,000 feet below.