The or Expo 70 was a world's fair held in Suita, Osaka Prefecture, Japan between March 15 and September 13, 1970. Its theme was "Progress and Harmony for Mankind." In Japanese, Expo '70 is often referred to as . It was the first world's fair held in Japan and in Asia The Expo was designed by Japanese architect Kenzō Tange, assisted by 12 other Japanese architects. Bridging the site along a north–south axis was the Symbol Zone. Planned on three levels, it was primarily a social space with a unifying space frame roof. The Expo attracted international attention for the extent to which unusual artworks and designs by Japanese avant-garde artists were incorporated into the overall plan and individual national and corporate pavilions. The most famous of these artworks is artist Tarō Okamoto's iconic Tower of the Sun, which still remains on the site today. Background Osaka was chosen as the site for the 1970 World Exposition by the Bureau International des Expositions (BIE) in 1965. 330 hectares in the Senri Hills outside Osaka had been earmarked for the site and a Theme Committee under the chairmanship of Seiji Kaya was formed. Kenzo Tange and Uzo Nishiyama were appointed to produce the master plan for the Expo. The main theme would be Progress and Harmony for Mankind. Tange invited 12 other architects to elucidate designs for elements within the master plan. These architects included: Arata Isozaki for the Festival Plaza mechanical, electrical and electronic installations; and Kiyonori Kikutake for the Landmark Tower. Master plan Two main principles informed the master plan. The first was the idea that the wisdom of all the peoples of the world would come together in this place and stimulate ideas; the second was that it would be less of an exposition and more of a festival. The designers thought that unlike previous expositions they wished to produce a central, unifying, Festival Plaza where people could meet and socialise. They called this the Symbol Zone and covered it and the themed pavilions with a giant space frame roof. The designers liked the idea that like the 1851 Great Exhibition in London, the roof of the Symbol Zone could be a unifying entity for the expo. They did not want the constraint imposed by the London Exhibition of having everything contained under one roof, so the space frame contained only the Festival Plaza and themed pavilions. Tange