The study of stonemasons’ marks in ancient constructions, a subject that has been systematically investigated since the 1980s to the present, tends to focus on a few standard uses and consider other seemingly random patterns as issues of preservation, leaving the archaeological potential of such marks largely untapped. This article presents a methodological approach to explain these apparently arbitrary patterns and a diachronic analysis of local labour organization at Sagalassos in south-western Turkey in four case studies: the Upper Agora, Lower Agora, Hadrianic Nymphaeum, and Makellon. The spatial analysis of the stonemasons’ marks and examination of the stone carving techniques and epigraphic data suggest that the different marks were either produced by the same individuals and/or formed part of the same construction process.

In Roman imperial times, metallurgy reached a high degree of specialization and complexity. The use of iron extended even to building technology, leading to some very particular results, achieving a sophisticated mastery of the technology with a complete understanding of metal properties, in a social and economic context characterized by large financial resources and a high level of creativity applied to architectural projects. A still unpublished device was found in the construction of several floors in the Villa of Giulia, Augustus' daughter, in Ventotene (Italy). In the thermal area, the concrete floors of the bath tubs are supported by an iron grid held in place by vertical iron posts strongly fixed in the underfloor, allowing both widespread hot air circulation and support for superimposed loads. A curvilinear metal grid supported by metal hooks was also used to obtain a tile-line vault, creating an interspace for the circulation of hot air in calidaria; a careful analysis of the remains of two vaulted systems in Villa Adriana, Tivoli (Italy), allows a clear reconstruction of this device. The building process was difficult and complex, requiring careful planning and great accuracy in execution. However, after nearly a century of experimentation, it is possible to propose the hanging ceiling built over the calidarium of the Baths of Caracalla in Rome as the most imposing example of the grid system ever realized.