Aquae Calidae, Bulgaria Aquae Calidae, Bulgaria Aquae Calidae (Latin for warm waters), also known as Therma and Thermopolis in the Middle Ages, was an ancient town in Thrace located in the territory of today's Bulgarian port city of Burgas. It was built around thermal baths using the hot springs and became one of the most important spa centres of ancient times. The site and baths of Aquae Calidae have been visited in the course of history by several important rulers from Philip II of Macedon to the Eastern Roman emperors Justinian I and Constantine IV, the Bulgarian ruler Terwel and the Ottoman Sultan
Roman Baths (Bath) legend was given great prominence as a royal endorsement of the waters' qualities, with the embellishment that the spring had cured Bladud and his herd of pigs of leprosy through wallowing in the warm mud. The name Sulis continued to be used after the Roman invasion, leading to the town's Roman name of "Aquae Sulis" ("the waters of Sulis"). The temple was constructed in 60–70 AD and the bathing complex was gradually built up over the next 300 years. During the Roman occupation of Britain, and possibly on the instructions of Emperor Claudius, engineers drove oak piles to provide a