Taipei 101 Now World's Tallest Building: "The CN-tower is the world's tallest free-standing structure (not building). The world's tallest structure is the KTHI-TV tower in North Dakota (629m) - it's supported by guy wires. The world's tallest structure not supported by guy wires is the Petronius Platform (640m) but since its sits in the ocean it can be argued that it is supported by buoyancy. The Council on Tall Buildings and Urban Habitat, who rate 'tall buildings', say the CN Tower isn't a building because it's not a 'frame structure made with floors and walls throughout' So, that leaves the CN Tower as the world's talles freestanding STRUCTURE."