Tokyo International Forum is located between Otemachi and Ginza, 3 minutes walk from the Yuraku-Cho Station. There are few halls and ball rooms manage to contain at least 20,000 audients. This new giant hall is popular for the international exhibition, world class famous singer concert and international convention.
If you are in the Marunouchi area, it is worth 20 minutes or so to experience the inside of the Tokyo International Forum. Designed by Rafael Vinoly, it is a wonderful espression of space and structure. Tokyo is full of Modern Architecture and if you are interested, I recommend 'The Japan Guide' by Botond Bognar and published by the Princeton Architecural Press. Architects whose works you may want to seek out are Tadao Ando, Kenzo Tange, Arata Isozaki, Toyo Ito, and Atsushi Kitagawara.