This article is concerned with emerging tourism valorisations of modern urban ruins with a focus on Berlin (Germany) and Detroit (United States). Leaning on a discussion of the notions of ‘ordinary’ and ‘extraordinary’, the paper analyses the processes of spatial (re)construction on which tourism appropriation of these marginal urban spaces is based. Ruin tourism questions the evolution of imaginaries and practices attached to modern urban ruins. Defined as frontiers for an increasingly ‘off the beaten tracks’ urban tourism, these spaces outline a range of issues related to the appropriation of the city space that reach far beyond the field of tourism.