We are building a series of fast, visually accessible, cross-sectional, hence static urban models for large metropolitan areas that will enable us to rapidly test many different scenarios pertaining to both short-term and long-term urban futures. We call this framework SIMULACRA which is a forum for developing many different model variants which can be finely tuned to different problem contexts and future scenarios. The models are multisector, dealing with residential, retail/service, and employment location, are highly disaggregate, and subject to constraints on land availability and transport capacities. They have an explicit urban economic focus around transport costs, incomes, and house prices and thus encapsulate simple market-clearing mechanisms. Here we will briefly outline this class of models, paying particular attention to their structure and the way physical flows and locations are mirrored by economic flows in terms of costs and prices. Several versions of the model now exist, but we will focus, first, on the simplest 'one-window' desktop pilot version with the most obvious graphical interface; and, second, on a much more elaborated framework developed for web access, extensible to web service architectures and other related services. To demonstrate its flexibility and intelligibility, we define the various interfaces and demonstrate how the aggregate model can be calibrated to the wider London region to which it is applied. We will demonstrate the model, albeit briefly with respect to the rapid assessment of different urban futures-"what-if " scenarios, based on the impact of new London airports in the Thames Estuary. The key feature of this entire project is that the model and its variants can be run in a matter of seconds, thus entirely changing the traditional dialogue associated with their use and experimentation. © 2013 Pion and its Licensors.