Constant Nieuwenhuys (1920–2005), known as Constant, was a founding member of the Cobra group and the Situationist International, and the artist behind the utopian architectural New Babylon project. This publication examines his practice in the 1950s and his transition from Cobra to New Babylon . In this decade, the fantasy figures of Constant’s Cobra period were followed by abstract painting, a transition from the two-dimensional to the three-dimensional plane with the architectural models and sketches made for the New Babylon project, and ultimately a return to painting with the color experiments that he pursued from 1969 until his death in 2005. Constant: Space + Colour gathers rarely seen works alongside a short selection of texts written between 1949 and 1965, which provide a glimpse into the radical transformations of these years.