Its popularity must have already spread across the entire empire when, in the 3rd century AD, Solinus described the baths of Aquae Sulis, modern-day Bath, in his Collectanea Rerum Memorabilium. The thermal complex was commissioned by Emperor Vespasian, although construction had already begun under Emperor Claudius during the Roman occupation, carried out by engineers and laborers who accompanied the army. The hot springs, which still flow today, emerge from the ground near the River Avon at a temperature of 46°C, inspiring awe and reverence long before the arrival of the Romans.

The name Aquae Sulis includes that of the native goddess Sulis, whose male-like face with Medusa-like features can still be seen on the temple pediment. Sulis is a Celtic name derived from Sul, meaning sun. However, of the pre-Roman sanctuarial phase, only the place name remains, as all traces of earlier activity were erased by the Roman monumentalization of the site. Like all imperial thermal complexes, Bath featured a calidarium, tepidarium, and frigidarium, three pools allowing bathers to transition from the natural hot spring water to cold water, passing through an intermediate temperature.

The thermal waters were believed to have healing properties, drawing pilgrims from all over Britannia to Bath in search of cures, aided by the many doctors located near the baths. Among them, oculists profited the most, as the very waters of the baths often caused infections and conjunctivitis, which they then treated on site. This led to the development of a lucrative market for eye specialists. One such oculist, Ianianus, has been identified through seals bearing his name on vials containing ointments for eye infections.

Numerous anatomical votive offerings left by pilgrims at the sanctuary have also been found, along with curse tablets, known as defixiones, which were thrown near the springs, places believed to offer the closest connection to chthonic and underworld deities.