The Mixed City has been a general principle of urban planning for decades. However, the metaphorical component of mixing has not been brought up yet, although metaphors are of high importance for the understanding of cities. Physicists categorize mixtures according to their grade of homogeneity and the aggregation state of the starting substances e.g. as alloy, aerosol, solution, agglomerate, emulsion or foam. These terms opened up the possibility to describe the disturbing experiences of modern metropolitan life. In the postwar decades they led to new interpretations of urban architecture. The protagonists shared a strong disapproval of the Functional City as codified in the Athens Charter. After all, since the turn of the millennium, mixing-metaphors have experienced a revival. In a manner of speaking, the modern dogma of urban separation was the crucial condition for the dream of a perfect mixture. Architects developed a sociologist-inspired concept of urbanity that was aimed at mixed-use as well as at socially and ethnically mixed urban communities. Via metaphors, these concepts became spatial and inspired architects to translate them into architecture. Based on selected examples, this article explores potentials and limitations of these mixing-metaphors.