Tokyo Sky Tree ups the ante

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The company building the Tokyo Sky Tree has raised expectations by announcing Friday that the tower will stand a record-breaking 634 meters tall when it is finished.

Initially scheduled to top out at 610 meters, Tobu Tower Sky Tree Co. was under threat of being left in the shade of another tower presently under construction in Guangzhou, China, and builders decided to extend the antenna on the very tip of the building by another 20 meters.

That will make it the world's tallest self-supporting tower.

Designed to be the new tower for terrestrial digital broadcasting throughout the greater Tokyo, and replacing the venerable -- but at 333 meters much smaller -- Tokyo Tower, the Sky Tree is scheduled to be completed in the spring of 2012.

As well as providing broadcasting links, the tower will have public observation decks and will be lit up every other night with different sets of lights.

"It will be beautifully decorated with a limited amount of lights, in consideration of the environment," lighting designer Hirohito Totsune told reporters.

Construction work is well under way, close to Oshiage Station in Tokyo's Sumida Ward, with the tower's triangular base already completed. The company's website indicates that work has reached a height of 174 meters. The completed building will have graceful curves that are meant to represent the blade of a samurai sword and other features found in traditional Japanese architecture.

An observation platform at a height of 350 meters will mark the point at which the structure changes from a triangular shape to a cylinder, which is better able to withstand very strong winds. A central shaft, made of reinforced concrete, draws its design from the five-tier pagodas that have dotted the Japanese landscape for hundreds of years -- and are remarkably effective in withstanding the potentially devastating effects of earthquakes.

A second observation deck will be at 450 meters above Tokyo, after which the remainder of the tower will rise to a height of 634 meters.

The tower is part of a major urban regeneration project that will include plazas, shopping and entertainment facilities and parks alongside the Kitajukken River.