Sostra fort was built around 147 AD at the order of Roman Emperor Antoninus Pius. The cohort II Mattiacorum of around 1000 soldiers (milliaria) was stationed here according to a statue base found in the principia, after being based at Sexaginta Prista (present-day Ruse) until 145 AD.The settlement (or vicus) to the west and east of the fort gradually grew into a town with a civilian population.
In 175 the road was improved under Marcus Aurelius, according to milestone inscriptions, leading to increased passing traffic and trade. It became a paved dual-width carriageway allowing two-way traffic.
From 235 another cohort (I Cisipadensium) was stationed here, consisting of nominally 500 men. The fort became the target of barbarian invasions and in 249 was captured by the Goths. In 254 another cohort was stationed here by emperor Gallienus and began building a new fort wall which continued till at least 282 under Claudius Gothicus, Aurelian and Probus.
In 378 the fort was again burnt down by the Goths, but in the late 4th century the christian basilica of St. George was built in the town. In the early 5th century eastern “barbarians” settled in Sostra and the nearby old Thracian strongholds in the mountains were restored.
It was completely destroyed by the Huns at the end of the 5th century.
The fortress is an impressive sightseeing very close to Golets, which usually takes about 15-20 min car drive.