CN Tower
"Guinness World Records" has called the CN Tower "the world's tallest self-supporting tower" and "the world's tallest free-standing tower". Although Guinness did list this description of the CN Tower under the heading "tallest building" at least once, it has also listed it under "tallest tower", omitting it from its list of "tallest buildings." In 1996, Guinness changed the tower's classification to "World's Tallest Building and Freestanding Structure". Emporis and the Council on Tall Buildings and Urban Habitat both listed the CN Tower as the world's tallest free-standing structure on land, and specifically state that the CN Tower is not a true building, thereby awarding the title of world's tallest building to Taipei 101, which is shorter than the CN Tower. The issue of what was tallest became moot when Burj Khalifa, then under construction, exceeded the height of the CN Tower in 2007 (see below).
The Towering Inferno
Architect Doug Roberts returns to San Francisco for the dedication of the Glass Tower, which he designed for contractor James Duncan. The Tower, 1,688 feet tall and 138 stories, is the world's tallest building. During pre-dedication testing, an electrical short starts an undetected fire on the 81st floor. Roberts suspects that Roger Simmons, the electrical subcontractor and also Duncan's son-in-law, cut corners. Roberts confronts Simmons, who reveals nothing.