until Roman times when Hissar developed into a large town and resort, called Dioclecianopolis, after the Roman emperor Dioclecian /284 – 305 AD/.
Many Roman ruins are still visible everywhere - public buildings, a small amphitheatre, the barracks of the Roman garrison, the foundations of a couple of the oldest churches in Bulgaria, as well as the best preserved Roman fortress in Bulgaria. The southern gate is known as "The Camels", because it had broken in the middle and looked like two camels facing each other, before it was partially restored in the late XX century.
After the fall of the Roman Empire, the prosperous city declined and when it was included within the borders of Bulgaria, it was just a minor fortified town. During the Turkish rule it further declined and at some point the once prosperous city was just a couple of small houses in the midst of many Roman ruins, which peasants from the nearby villages used for a stone quarry, destroying most of them in the process.
There are 22 mineral springs in Hissar - 16 natural and 6 deeply drilled with temperatures ranging from 37 to 51 degrees C. Their water has a low mineral level - 0.257 g/l, hydrogen carbonate-sulfate, chlorine and sodium, fluorine-silicic, alkaline. It has a high pH level - 9. It has not got colour or smell. It is with pleasant taste. Hissar mineral water can be used both as table water and for prevention of: gastro-intestinal tract diseases; nephrolithiasis and nephro-urological diseases; cholelithiasis; locomotory system diseases; gynecological diseases; dental diseases and prevention of dental caries; chronic intoxication with heavy metals and pharmaceutical substances.
There are many interesting places you can visit in Hissar and its surroundings: Archaeological reserve and museum in the town; Thracian tombs in the village of Starosel.
You may take part in the rich cultural calendar, parts of which are: Annual festival of the theatrical nonprofessional formations; Masked festival procession in February; Holidays of mineral water at the beginning of June; Rose holiday in Starosel village.
The offers for adventures in Sredna gora mountain are for the lovers of nature. These are protected peculior, rock formations and caves, forest shrines.