Michael Batty is Bartlett Professor of Planning at University College London where he is Chair of the Centre for Advanced Spatial Analysis (CASA). He has worked on computer models of cities and their visualisation since the 1970s and has published several books, such as Cities and Complexity (MIT Press, 2005) which won the Alonso Prize of the Regional Science Association in 2011, and most recently The New Science of Cities (MIT Press, 2013). His blogs www.complexcity.info cover the science underpinning the technology of cities and his posts and lectures on big data and smart cities are at www.spatialcomplexity.info . His research group is working on simulating long term structural change and dynamics in cities as well as their visualisation. Prior to his current position, he was Professor of City Planning and Dean at the University of Wales at Cardiff and then Director of the National Center for Geographic Information and Analysis at the State University of New York at Buffalo. He is a Fellow of the British Academy (FBA ), the Academy of Social Sciences (FAcSS ) and the Royal Society (FRS ), was awarded the CBE in the Queen’s Birthday Honours in 2004 and the 2013 recipient of the Lauréat Prix International de Géographie Vautrin Lud (generally known as the  'Nobel de Géographie') . This year 2015 he received the Founders Medal of the Royal Geographical Society for his work on the science of cities. In 2016 he received the Gold Medal of the Royal Town Planning Institute, and the Senior Scholars Award of the Complex Systems Society. He has Honorary Doctorates form the State University of New York and from the University of Leicester.

In the fields of architecture and planning, 3D models primarily representing the physical form of buildings and cities, came hard on the heels of computer cartography and 2D mapping. In this paper, we will review how geographic information systems rapidly acquired the ability to simulate urban form in 3D and how these ideas then moved on to incorporate various kinds of virtual reality and virtual worlds as an integral part of this representation. Currently many ideas associated with the metaverse are being developed and the notion of a 3D model as a fairly accurate portrayal of a ‘real’ building to a ‘real’ city is being rapidly relaxed. We review this transition from 2D to 3D and the ways different elements of the city, much being fashioned from data streamed in real time, are being incorporated into such models. We illustrate this evolution with our model of Virtual London (ViLo) and we then contrast this with other models that focus on London but are much more focussed on urban processes than on visual representation. In this sense, the different models focus on the same place and as such they are digital twins of one another. This paper will focus on how very different kinds of models in 2D and 3D relate to one another suggesting that in the future, the idea of many models of the same place being built – many twins of each other – will become the norm as developing such models becomes ever easier to construct and as data for their form becomes ever more available through various kinds of sensing.