During the past 5 years, a full coverage geophysical survey of the intra-mural and parts of the extra-mural areas of the deserted Roman town of Ammaia (Portugal) was achieved. Using a wide array of instruments, this approach allowed an in depth analysis of a newly founded Roman centre, linking the excellent survey data with stratigraphic information, obtained via earlier excavations and focused ground truthing operations. Together with data from the study of finds, this large project now allows to approach the urbanism of a very regularly built Roman town. An attempt is made here to delineate the foundation process, and identify the main steps undertaken by the planners.