This article focuses on the ‘Digital Wall’, a project created by the City of Curitiba (Brazil) to integrate algorithmic surveillance technologies into its local law enforcement agency, including AI-powered facial recognition. We depart from a political economical framework which integrates the work of the geographer Milton Santos with a wider literature on smart cities and surveillance. We find that the Digital Wall aptly combines the fable of ‘smart cities’ – the continuous datafication of urban space – with fears around security and violence. This fable, as we analyse, draws social legitimacy and public investment for surveillance technologies. We then unravel the materiality of the Digital Wall's perversities, including the public-private partnerships in its development, as well as how it is further used as a ‘showcase’ for a new paradigm of a (walled) smart city.