This AD Round Up is dedicated to unbuilt classics, a selection of projects and ideas that, although never built, contributed greatly to the canon of twentieth century architecture. In 1920, Buckminister Fuller designed the Dymaxion House, which displayed forward-thinking innovations in sustainability and prefabrication. In 1924, Le Corbusier’s radical plan for Ville Radieuse (The Radiant City) had an extensive inﬂuence upon modern urban planning and led to the development of new high-density housing typologies. In the same year Friedrick Kiesler introduced his "Endless House", the basis for his subsequent manifesto of Correalism. Eight years later in 1932, Philip Johnson and Henry-Russell Hitchcock curated the “Modern Architecture: International exhibition” at the MoMA, introducing the emerging International Style and laying the principles for Modern architecture. And finally, one of Archigram’s most famous utopian visions, the Plug-In City, proposed by Peter Cook in 1964, offered a fascinating new approach to urbanism and reversed traditional perceptions of infrastructure’s role in the city.