The Thermae (Baths) were discovered during excavations in 1973 - 1975 and lately in 1998-2001. It is supposed that they were built in 6th century during the reign of the Byzantine emperor Justinian I the Great (527-565). Till date around 2/3 of the area has been investigated and the rest of it lies under the streets and houses nearby. 

There are five warm premises visible: two of them with semi-circled pools, a central hall and a corridor. The walls of the thermae are built in “opus mixtum” and riveted with marble and are up to 3m high. The warm premises possess of pendant floor and hypocaust system for heating. The central hall is the most impressive one, where four massive marble columns with Corinthian capitals supported a cruciform dome. The floor was covered with marble pavement. The thermae were water supplied by a special water-conduit from the western side of the building. In the period 5th – 6th century a water supply underground system was constructed for the entire town. The baths functioned until the end of 8th century. 

After that some reconstruction works were made: a brick wall was built in the corridor to narrow it. In the beginning of 9th century, the thermae were reconstructed to serve for housing and agricultural needs. Limekilns were built in the central hall. The two Byzantine chroniclers Theophanes the Confessor and Nikephoros I marked that in 680 the Byzantine Emperor Constantine IV Pogonat used to cure his legs here.