The favourable climate and thermal springs were the reasons why people settled the site in the hoary antiquity. There was a prehistoric settlement here already in theV-IV millennium BC.The life around the springs has never stopped ever since. In the V-IV C BC the Thracian settlement at that place belonged to the Odryssian Kingdom.The big Thracian cult buildings found near village of Starossel are dated to that period.
After the Romans conquered the province of Thrace in 46 AD, a big Roman settlement emerged around the mineral springs. In 293 the emperor Diocletian declared it town and the citizens began to fortify it by solid walls and to develop new town plans. The architecture and fortifying system of the Roman town Diocletianopolis are among the most original and well preserved in Europe. In many places the fortress wall reaches 11 m height, and the south gate rises to 13 m. A lot of buildings are concentrated in the central park of the modern town "Maiden's tears".
Here is the most representative public building (residence). It is a big two-storied edifice and its rooms are vaulted with impressive arched construction. A bath complex, spread on 2000 m2 is situated nearby. The thermae of Diocletianopolis were used for mineral water procedures and treatment. They are one of the very few Roman therms of this kind found on the Balkan Peninsula. The original and impressive thermae are preserved almost up to the roof. From within the rooms were faced with marble and the hot water was used for heating. The complex of the impressive buildings in "Maiden's tears" park also includes an amphitheatre. It was one of the most favourite places for the people of those remote ages, who visited Diocletianopolis for recreation and amusement. The amphitheatre in Diocletianopolis is of a circus type, used for sport activities and animal fighting, it was built in the first half of the IVth century, when people observed the new Christian cannons not to shed human blood. The arena and the service rooms are preserved in an excellent condition.
After the Christianity was accepted as an official religion in the Roman Empire in the first decades of the IVth century AD, Diocietianopolis became an important Christian centre - a bishop's seat. So far ten Early Christian basilicas have been excavated within and outside the fortress walls. They are indicative for the characteristics of the Early Christian architecture development. This could be seen even today in the Early Christian churches, which are well preserved and exhibited. The remains of a unique by now two-aisled basilica have been discovered here. It had been built in the middle of the Vth century in the barrack complex of the ancient town. In the historical sources Diocletianopolis is mentioned as the third biggest town in the province of Thrace after Philippopol (Plovdiv) and Beroe (Stara Zagora).
The archaeological excavations have brought about the locating of five cemeteries, which belonged to ancient Diocletianopolis. About 300 m south from the fortified town is situated the Roman tomb. It is preserved in original and it is open for visitors. It impresses with its long vaulted corridor and the mosaic floor of the grave chamber.