Roman Cadastral Plans (formae) Definition, Evidence, and Boundary Representation

By adopting a multidisciplinary and comparative approach, integrating archaeological and epigraphical evidence with the information provided by the writings of the Roman land surveyors (Gromatici veteres), this article investigates the nature of the Roman cadastral plans (formae), their function, and the depiction of internal boundaries and external borders in them. It addresses fundamental questions regarding the surviving material evidence, the accessibility of the formae, and the specific role played by supplementary records, such as the tabulae aeris and the libri aeris. The authors argue that Roman formae were sophisticated multimodal tools where graphic conventions, such as orthogonal grids and curving lines, directly corresponded to the legal status of land, whether centuriated or not (e. g., subseciva, agri occupatorii or arcifinii/-ales). While public bronze formae served as authoritative evidence for the state, the article highlights the overlooked category of private, unofficial maps used by single individuals to manage unsurveyed land. This work offers the first comprehensive overview of the evidence for Roman formae and introduces new interpretations by identifying the bronze tablet from Ilici as a potential tabula aeris and proposing a pottery fragment from the Iberian Peninsula as a possible surviving example of a private forma.