the 1964 Summer Olympics and 1964 Summer Paralympics, the 2020 Summer Olympics and 2020 Summer Paralympics (postponed; held in 2021), and three summits of the G7 (in 1979, 1986, and 1993). Tokyo is an international research and development hub and is likewise represented by several major universities, most notably the University of Tokyo. Tokyo Station is the central hub for Japan's high-speed railway network, the Shinkansen; Shinjuku Station in Tokyo is also the world's busiest train station. Notable special wards of Tokyo include: Chiyoda, the site of the National Diet Building and the Tokyo Imperial Palace; Shinjuku, the city's administrative center; and Shibuya, a commercial, cultural, and business hub. Etymology Tokyo was originally known as , a kanji compound of 江 (e, "cove, inlet") and 戸 (to, "entrance, gate, door"). The name, which can be translated as "estuary", is a reference to the original settlement's location at the meeting of the Sumida River and Tokyo Bay. During the Meiji Restoration in 1868, the name of the city was changed to , when it became the new imperial capital, in line with the East Asian tradition of including the word capital () in the name of the capital city (for example, Kyoto (), Keijō (), Beijing (), Nanjing (), and Xijing ()). During the early Meiji period, the city was sometimes called "Tōkei", an alternative pronunciation for the same characters representing "Tokyo", making it a kanji homograph. Some surviving official English documents use the spelling "Tokei"; however, this pronunciation is now obsolete. History Pre-1869 (Edo period) Tokyo was originally a village called Edo, in what was formerly part of the old Musashi Province. Edo was first fortified by the Edo clan, in the late twelfth century. In 1457, Ōta Dōkan built Edo Castle. In 1590, Tokugawa Ieyasu moved from Mikawa Province (his lifelong base) to the Kantō region. When he became shōgun in 1603, Edo became the center of his ruling. During the subsequent Edo period, Edo grew into one of the largest cities in the world with a population topping one million by the 18th century. Edo was still the home of the Tokugawa shogunate and not the capital of Japan (the Emperor himself lived in Kyoto almost continuously from 794 to 1868). During the Edo era, the city enjoyed a prolonged period of peace known as the Pax Tokugawa, and in the presence of such peace, the shogunate adopted