Accurate mapping of the 78-ha Roman town of Viroconium (modern-day Wroxeter in Shropshire, UK) in preparation for detailed research and site management proved a task that requires the use of modern information techniques. This article describes the creation of high spatial accuracy maps by the use of GPS-located gradiometer survey data in order to georeference available aerial photographs, and the use of digital processing of aerial photographs to obtain additional information invisible to the unaided eye. A GIS is being used to build a vectorized interpreted map of the town with a spatial error typically less than one metre. The results compare favourably with previous mapping efforts based on traditional methods.