Located on the outskirts of the Sredna Gora mountain range, about 40 km north of Plovdiv, in Central Bulgaria, lies the ancient town of Hisarya, famous for its nearly two dozen mineral springs. This small wonder of nature has been attracting people since the prehistoric times, with traces of settlement here that dates back to at least the 4th century BC. It’s the healing waters of Hisarya’s springs and its pleasant climate that brought the Romans to this place in 46 AD. The Romans overthrew the Thracians and Hisarya became a Roman town. Not much happened for the next two hundred and fifty years, until Emperor Diocletian decided to promote Hisarya to the status of a Roman city, and renamed it Diocletianopolis. At once, there were constructions all over Hisarya as the small town tried to adapt itself to the prestigious role. Buildings and bath house were built, and streets were laid, but the most striking construction to take place were the massive fortification walls around the city. Ref.: https://www.amusingplanet.com/2016/10/the-ancient-roman-walls-of-hisarya.html