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).
Guangzhou International Finance Center
Guangzhou International Finance Centre or Guangzhou West Tower, is a 103-storey, skyscraper at Zhujiang Avenue West in the Tianhe District of Guangzhou, Guangdong. One half of the Guangzhou Twin Towers, it is the 17th tallest building in the world, completed in 2010. As of March 2018, it is the world's tallest building with a roof-top helipad, at 439 m (1,439 feet) high. The world's second-tallest building with a roof-top helipad was also completed in 2010: Beijing's China World Trade Center Tower III, whose roof-top helipad is 330 m (1,083 feet) high. Both buildings are taller than the U.S. Bank Tower, the previous record-holder from 1989 to 2010, whose roof-top helipad is only 310.3 m (1,018 feet) high.