concepts of regeneration. Although Metabolism rejected visual references from the past, they embraced concepts of prefabrication and renewal from traditional Japanese architecture, especially the twenty-year cycle of the rebuilding of the Ise Shrine (to which Tange and Kawazoe were invited in 1953). The sacred rocks onto which the shrine is built were seen by the Metabolists as symbolising a Japanese spirit that predated Imperial aspirations and modernising influences from the West. In his Investigations in Collective Form Maki coined the term Megastructure to refer structures that house the whole or part of a city in a single structure. He originated the idea from vernacular forms of village architecture that were projected into vast structures with the aid of modern technology. Reyner Banham borrowed Megastructure for the title of his 1976 book which contained numerous built and unbuilt projects. He defined megastructures as modular units (with a short life span) that attached to structural framework (with a longer life span). Maki would later criticise the Megastructure approach to design advocating instead his idea of Group Form which he thought would better accommodate the disorder of the city. The architect Robin Boyd readily interchanges the word Metabolism with Archigram in his 1968 book New Directions in Japanese Architecture. Indeed, the two groups both emerged in the 1960s and disbanded in the 1970s and used imagery with megastructures and cells, but their urban and architectural proposals were quite different. Although utopian in their ideals, the Metabolists were concerned with improving the social structure of society with their biologically inspired architecture, whereas Archigram were influenced by mechanics, information and electronic media and their architecture was more utopian and less social. Osaka Expo, 1970 Japan was selected as the site for the 1970 World Exposition and 330 hectares in the Senri Hills in Osaka Prefecture were set aside as the location. Japan had originally wanted to host a World Exposition in 1940 but it was cancelled with the escalation of the war. The one million people who had bought tickets for 1940 were allowed to use them in 1970. Kenzo Tange joined the Theme Committee for the Expo and along with Uso Nishiyama he had responsibility for master planning the site. The theme for the Expo became "Progress and Harmony for Mankind". Tange invited twelve architects, including Arata Isozaki, Otaka and Kikutake to design individual elements. He also asked Ekuan to oversee the design of