At 92 years of age, for his entire career Yona Friedman has occupied an unusual spot within the architecture world; his signature concept, the Ville Spatiale which he first proposed in 1956, combines the top-down megastructural thinking visible in later projects such as Archigram's Plug-In City with a total freedom for occupants to design and build their own homes within the structure. In this installment of his “City of Ideas” column, Vladimir Belogolovsky interviews Friedman at his home in Paris to talk about the Ville Spatiale and his theories of mobile and improvised architecture.