Where holes in our interpretation remain, we turn to examples of buildings of similar ground plan and function from later historical periods to find further possibilities. Once we have gathered the possible details, and their variables, of the building’s form and composition, we create our models. Without the 3D software, this process is particularly slow and limited in perspective. We are constrained to drawing certain views of the structure and, often, without the added visual details (wall facing, entablatures, roof tiles, etc) which really affect the presentation of the building itself. The 3D modelling process enables us to reconstruct a building with minute detail and allows us to see the building from various angles. An added bonus is the ability of easily changing the unit of measure from our modern metric system (in which the surviving remains on site are measured) to the Roman foot (which equals 0.296 m) to check for Roman design units. Best of all, we can place the building within the greater model of the site to see how the buildings interact with one another, giving us a better understanding of a Roman person’s experience of Portus. Once our model is completed, we test its structural stability to see if our interpretations stand up to reality. If they don’t, we go back to the drawing board and begin again.