Tallest structures
Warsaw radio mast, the height record holder from 1 974 to 1 991
The CN Tower in Toronto, Ontario, Canada, was the world's tallest freestanding structure from 1 975
to 2007.
This category does not require the structure to be "officially" open but does require it to be "topped
out".
The tallest artificial structure is Burj Khalifa, a skyscraper in Dubai that reached 829.8 m (2,722 ft) in
height on January 1 7, 2009.[2] By April 7, 2008 it had been built higher than the KVLY-TV mast in
North Dakota, USA.[3] That September it officially surpassed Poland's 646.38 m (2,1 20.7 ft) Warsaw
radio mast, which stood from 1 974 to 1 991 , to become the tallest structure ever built. Guyed lattice
towers such as these masts had held the world height record since 1 954.
The Petronius Platform stands 61 0 m (2,000 ft) off the sea floor leading some, including Guinness
World Records 2007, to claim it as the tallest freestanding structure in the world. However, it is
debated whether underwater height should be counted, in the same manner as height below ground
is ignored on buildings. The Troll A platform is 472 m (1 ,549 ft), without any part of that height being
supported by wires. The tension-leg type of oil platform has even greater below-water heights with
several examples more than 1 ,000 m (3,300 ft) deep. However, these platforms are not considered
constant structures as the vast majority of their height is made up of the length of the tendons
attaching the floating platforms to the sea floor. Despite this, Guinness World Records 2009 listed the
Ursa tension leg platform as the tallest structure in the world with a total height of 1 ,306 m (4,285 ft).
The Magnolia Tension-leg Platform in the Gulf of Mexico is even taller with a total height of 1 ,432 m
(4,698 ft).