Taking as its point of departure the preeminent association between momentary experience and urban existence, this chapter expands on how the modern city’s relationship to temporariness is conceived by approaching it through particular forms of temporary urban space. It focuses in turn on several sites that emerged (and subsequently vanished) in the early twentieth century, each of which embodies a metropolis in microcosm: the White City exhibitions, the trench system on the Western Front, and the elaborate sets that were constructed for an expanding British film industry. In drawing a connection between literature’s interest in temporariness in this period and the pseudo-cities that parallel it – exhibitionary, military, and cinematographic – the chapter charts how responses to urban ephemera in the work of such writers as Isaac Rosenberg, Ford Madox Ford, May Sinclair, and Katherine Mansfield are inflected through these spaces, as well as how such responses evolve across the century’s opening decades.