Megastructure is an architectural and urban concept of the post-war era, which envisions a city or an urban form that could be encased in a massive single human-made structure or a relatively small number of interconnected structures. In a megastructural project, orders and hierarchies are created with large and permanent structures supporting small and transitional ones.

Metabolism was a post-war Japanese biomimetic architectural movement that fused ideas about architectural megastructures with those of organic biological growth. It had its first international exposure during CIAM's 1959 meeting and its ideas were tentatively tested by students from Kenzo Tange's MIT studio.