The concept of heterotopia was introduced and immediately abandoned by Michel Foucault in 1966-67, but it quickly diffused across human geography, urban theory, and cultural studies during the 1990s. Notwithstanding the deserved impact of Foucault's overall work on these fields, there are some conceptual problems with the heterotopia concept. While the desire for a single term to probe spatial difference is understandable, the author takes issue with the kind of space envisioned in heterotopology. From a close reading of Foucault's notes, and with the help of Deleuze, Derrida, and Althusser, it is suggested that the spatiality of Foucault's heterotopology repeats certain flaws of the structuralism in vogue in 1960s France. In order for heterotopias to be 'absolutely different' from 'all the rest' of space, Foucault needs to posit a totality to society and to perform a 'slice of time'. The author ends by briefly examining how the structuralist tendency of heterotopology has pervaded some recent Anglophone adoptions of Foucault. As both geography and postcolonial theory have shown, slicing time often conceals particularist suppositions and is therefore inadequate to account for the multiplicity and unevenness of geographical change.