This book presents the most important results of the European funded project RADIO-PAST or "Radiography of the Past. Integrated non-destructive approaches to understand and valorise complex archaeological sites". In order to develop non-invasive approaches to investigate, interpret, visualize and valorize complex archaeological sites, the researchers of the project have selected the site of Ammaia, a deserted Roman town in Portugal, as an "open laboratory" for intensive field research. Here innovative approaches ranging from field archaeology to geomorphology, from remote sensing to geophysical survey, from ICTs to Cultural Heritage management, have lead to an exemplary study of a lost Roman town. This research effort is part of a wider trend all over the ancient world to study abandoned Roman towns using a wide array of modern survey methods. When combined with more established approaches, such as stratigraphic excavations and the study of legacy data, these methods can produce a much more complete vision on urbanism under Roman dominance.