A new branch of the Anio novus aqueduct (Rome, Italy) revealed by archaeology and geophysics

The area south-east of Rome is characterised by the presence of several roman aqueducts which brought water to the eternal city from the Apennine and Alban Hills springs. In the last 40 years, several pieces of evidence about these aqueducts were acquired during the realisation of archaeological test trenches before building activities. In 2019, a small branch of a subterranean aqueduct unknown to the Latin sources was unearthed in Via dei Sette Metri. Here we show that this aqueduct is a lateral branch of the Anio Novus, a major imperial aqueduct built between 38 and 52 CE. To achieve this result, we employed detailed photogrammetric restitution of the new aqueduct and an integrated geophysical survey focused in the area where the Anio Novus was supposed to pass. Electrical Resistivity Tomography (ERT) and Ground Penetrating Radar (GPR) methods were used to reconstruct aqueduct paths and their relative heights. Different light conditions were tested during the picture acquisition step to determine the best practice in the photogrammetric restitution. The results obtained in this study confirmed the great effectiveness of the integration between geophysical investigation methods and the modern archaeology approach in detecting buried ancient structures.