The CN Tower in Toronto, Ontario was the world's tallest freestanding structure on land from 1975 until the Burj Dubai surpassed it in 2007, rising 553.33 m (1,815 ft). It is currently the world's tallest completed freestanding structure on land.

The tallest standing structure is the KVLY-TV mast 30 miles (48 km) north of Fargo, North Dakota United States, at 628.8 m (2,063 ft). It is a transmission antenna, consisting of a bare metal structure supported by guy-wires.
Transmission antennas of this type are not usually included with the world's tallest buildings because they are not self-supporting. The issue is further complicated if all manmade habitable structures are considered. Under that criterion it is possible to claim 'tallest structure' records for deep mine-shafts, or the Mohole drilling rig, which can be several miles (8-10 km) in vertical length.

The CN Tower in Toronto, Ontario was the world's tallest freestanding structure on land from 1975 until the Burj Dubai surpassed it in 2007, rising 553.33 m (1,815 ft). It is currently the world's tallest completed freestanding structure on land.
The CN Tower in Toronto, Ontario, Canada, standing at 553.3 m (1,815 ft), was the world's tallest freestanding structure on land from 1976 until September 12, 2007, when it was overtaken in height by the rising Burj Dubai.[1] It has the world's highest public observation deck at 446.5 m (1,465 ft). It remains the world's tallest completed freestanding structure, pending the Burj Dubai's completion (projected for mid 2009).
The Petronius Platform stands 610 m (2,001 ft), leading some to claim it as the tallest freestanding structure in the world. However, as this oil and natural gas platform is partially supported by wires, critics argue that it is not freestanding, and the below-water height should not be counted, in the same manner as underground 'height' is not taken into account in buildings.
The Troll A platform is 472 m (1,549 ft), without any part of that height being supported by wires.
Taipei 101 in Taipei, Taiwan is currently the world's tallest inhabited building in three out the four main categories that are commonly measured: at 509.2 m (1,671 ft) as measured to its architectural height as well as roof height 449.2 m (1,474 ft) and highest occupied floor 439.2 m (1,441 ft). The Sears Tower is highest in the last category: the highest current height to the top of antenna of any building in the world at 527.3 m (1,730 ft).
The Burj Dubai, currently under construction, is already the tallest freestanding structure on land. As of 5 February 2008, the tower's developers reported its height to be 604.9 m (1,985 ft), with 159 completed floors,[2] surpassing Taipei 101 as the tallest building.[3] On its completion in 2008 or 2009 it will break the height record in all four categories for completed buildings by a wide margin. While the final height has not been released to the public, the developers state that the building will be at least 818 m (2,684 ft) including the spire. The developer, Emaar, is keeping structural details secret due to competition for the "world's tallest" with other proposed buildings, including the nearby Al Burj.[4] The CN Tower will maintain its record of the world's highest observation deck as Burj Dubai's deck will be at 442 m (1,450 ft).[5] The 'Symbol of Dubai' will have more than 160 floors, 56 elevators, apartments, shops, swimming pools, spas and corporate suites.