The work of Constant Nieuwenhuys, New Babylon was a fantastic vision of a new city overlaid above the existing city, much like some of the places described in Invisible Cities. Constant was part of the Situationist International for some time, and New Babylon spatialised and made concrete many of the Situationist ideas around revolutionary socialism and the transformative potential of emotion and play over work and rationalism. [Many more pics if you follow the link and scroll down]

Architect and theorist Lebbeus Woods has this to say:

New Babylon was inspired by and contributed to the work of the Situationists, a group of intellectuals, theorists and writers, as well as artists who were anything but Modernists in the classic capitalist mold. They were inspired by the irrational forms and practices of Dada and Surrealism, and were what we could call neo-Marxists, meaning inspired by Marx’s vision of revolutionary socialism but seeking to use the capitalist system to achieve their ends. Guy Debord and others invented tactics such as derive, psychogeographie, and detournment, which seized upon, then subverted, capitalist notions in order to develop radical ways of living that were meant to culminate in revolution (Archigram first heard of these through Constant’s lecture, no doubt). Constant joined the Situationists early on and became their architect, much the same as Antonio Sant’Elia had done with the Futurists, half a century before. The spaces of New Babylon were intended to be spaces of disorientation and of reorientation, from rational, functionalist society to one that is liberated and self-inventing. It was meant to replace capitalist exploitation of human labor and emotion with anarchist celebration of them.  Its architecture was to provide a complex armature on which could be woven endlessly new, unpredictably personal urban experiences, determined by ever-changing individual desires. In the end, however, the architecture of the New Babylon seemed to overwhelm such playful, radical spontaneity by its sheer weight and monumental scale.