The Petronas Twin Towers in Kuala Lumpur, Malaysia are twin towers and were the world's tallest buildings before being surpassed by Taipei 101. However, the towers are still the tallest twin buildings in the world. They were the world's tallest buildings from 1998 to 2004 if measured from the level of the main entrance to the structural top, the original height reference used by the US-based Council on Tall Buildings and Urban Habitat from 1969 (three additional height categories were introduced as the tower neared completion in
The Petronas Twin Towers were the tallest buildings in the world until Taipei 101 was completed in 2004, as measured to the top of their structural components. Spires are considered integral parts of the architectural design of buildings, to which changes would substantially change the appearance and design of the building, whereas antennas may be added or removed without such consequences. The Petronas Twin Towers remain the tallest twin buildings in the world.
The Willis Tower and the World Trade Center towers were each constructed with 110 occupied floors – 22 more than the Petronas Twin Towers’ 88 floors. The Willis Tower and the World Trade Center’s roofs and highest occupied floors substantially exceeded the height of the roof and highest floors of the Petronas Twin Towers. The Willis Tower’s tallest antenna is 75 m (246 ft) taller than the Petronas Twin Towers’ spires.
However, in accordance to CTBUH regulations and guidelines, the antennas of the Willis Tower were not counted as part of its architectural features. Therefore, the Petronas Twin Towers exceed the official height of the Willis Tower by 10m, but the Willis Tower has more floors with occupied office space at a higher level.