The city has hosted multiple international events, including the 1964 Summer Olympics and Paralympics, the postponed 2020 Summer Olympics and Paralympics and three G7 Summits (1979, 1986, and 1993). Tokyo is an international center of research and development and is represented by several major universities, notably the University of Tokyo. Tokyo Station is the central hub for Japan's Shinkansen bullet train system, and the city is served by an extensive network of rail and subways. Notable districts of Tokyo include Chiyoda (the site of the Imperial Palace), Shinjuku (the city's administrative center), and Shibuya (a commercial, cultural and business hub).