The presence of a Roman thermal site located in close proximity to the Bagno Grande (Great Bath) pools at San Casciano dei Bagni (SI) has been known since 1585. Following extensive field surveys in 2016-17, geophysical surveys in 2018 proved the consistent presence of archaeological structures covering an area of over 4 hectares. In 2019, excavations began south of the Medici pools and brought to light an Etruscan and Roman sanctuary. The excavations are uncovering the structures facing the spring from which 25 litres of water per second flow continuously at 42°C. They belong to an elongated building, more or less rectangular, at the centre of which a travertine pool in the shape of a ‘bone’ was built in the Tiberian period on top of an earlier Etruscan pool. From the 3rd century BCE to the 5th century CE (when the entire sanctuary complex was dismantled), the sacred pool contained votive offerings. The votive deposit in the pool reflects the building phases of the sanctuary with moments of obliteration alternating with ritual depositions. Between the 2nd and the 1st centuries BCE numerous bronze statues were placed in the sacred spring, together with vegetal offerings; while from the mid-1st century CE, coins became the most common offering.