A few metres up-hill from where the temple to the Great Mother would have been located, there’s a yellow building known as the High-Courier’s Palace and underneath it the ruins of the Roman baths of the Cassiuses. Or so it is told when, in the aftermath of the Great Earthquake of 1755, construction workers came across the ruins of a Roman building in 1771, along with an inscription which started with the words THERMAE CASSIORVM (Hübner 1871, 12). The text has led some to point out Quintus Cassius Longinus, governor of Hispania in 44 BCE, and his brother Lucius as the patrons of those baths, but this theory has been challenged, as there are other known cassiuses from Olisipo (Moita 1994, 48). Existing street names may also hint at a hot spring: there’s the Rua das Pedras Negras (Street of the Black Stones), which some believe to refer to darkened rocks from a thermal spring.
A harder case is that of the Roman galleries, a subterranean structure in downtown Lisbon that was also discovered in 1771 during the reconstruction works of the city. They were once believed to have been baths, but currently they’re seen as a cryptoporticus, built on the river banks in order to support large (probably public) buildings.
One of the reasons why the galleries were initially seen as ruins of Roman baths was the discovery of a votive inscription to Aesculapius on the spot. Currently on display at the National Archaeology Museum, it reads SACRVM AESCULAPIO M. AFRANIVS EVPORIO ET L. FABIUS DAPHINVS AVG. MVNICIPIO D. D. (Hübner 1871, 8), which translates as “Sacred to Aesculapio, Marcus Afranius Eporio and Lucius Fabius Daphinus, Augustales, gave as offering to the municipality”.
It is not certain if the inscription was used as construction material or was really intended to be placed in the galleries, which are dated from the 1st century. Guardado Silva notes the existence of a nearby chapel to Our Lady of the Olive Tree, destroyed in 1755, but known in the medieval period for a spring with healing properties (2008, 44; see also Moita 1994, 50). It is therefore not impossible that some of the construction area provided by the cryptoporticus would have been used for a shrine to Aesculapius, though its dimension and whether or not it included baths is completely unknown. Another votive inscription to the God of Medicine was discovered in the middle of the 18th century after the demolition of part of the medieval wall close to where the Iron Gate once stood (red dot and line). According to Vieira da Silva (1944, 131; n. 31), it read AESCVLAPIO AVG SACRVM CVL TORES LARVM MALIAE ET MALIOLI M. COSSVTVIS MACRINVS DONAVIT (“Sacred to Augustian Aesculapius. Marcus Cossutius gave it to the devotees of the Lares of Malia and Maliolo”). It is assumed that it came originally from the Baths of the Cassiuses, and there are news of two more found in the Street of the Black Stones (Leite de Vasconcelos 1913, 263) and one in the church of Saint James in the 17th century, though there are doubts about the latter (Moita 1994, 53).