Tokyo Big Sight convention center in Japan. It opened in 1996.
Similarly to the Ed-Tyokyo Museum, the pedestrian level is opened up by 4 massive towers that lift up the main building. It has three main areas: the conference center, and the east and west exhibition halls. The most historically basic architecture shape is the pyramid. It is flipped upside down and arranged in a square with connections in between.
More Info , More Images , More Info and Images
Video: Atrium , View from bottom