Tokyo Skytree is the tallest structure in Japan and with its full height of 634.0 meters, it is the tallest tower in the world. Twice as tall as the Eiffel Tower, it is only the second tallest structure in the world after Burj Khalifa (829.84 m). Led by Tobu Railway and a group of six terrestrial broadcasters headed by NHK, the tower project forms the centerpiece of a large commercial development in northeastern Tokyo with a reported cost of 44 billion yen. The project was completed on 29 February 2012 and the tower was open to the public on 22 May 2012.
One of its main purposes is to relay television and radio broadcast signals since the Tokyo Tower (which is used to be the tallest tower in Tokyo areas with a height of 333 m) is now surrounded by many high-rise buildings. According to some news report, an estimated 200,000 people braved heavy rain on that day to watch this newest attraction in the Japan’s capital.
http://www.tokyo-skytree.jp/en/index.html