Ancient Town Colonia Ulpia Oescus

Roman rule in the region between the Balkans and the Danube was established in 29 and 28 BC. Between 14 and 11 BC, a system of fortifications was built on the right bank of the Danube, to which Oescus likely belonged due to its strategic location. From the late Augustan period, epigraphic sources indicated a camp of the Legio V Macedonica in Oescus. By 33 AD at the latest, the Fifth Macedonian Legion was stationed here. During Trajan's Dacian Wars, Oescus played an important role as a base. Around 167 AD, the settlement was elevated to Colonia Ulpia Oescus, granting it the highest city rights status in the Roman Empire. The city experienced its first flourishing period in the 2nd century, marked by intensive construction activity. From 238 AD, barbarian invasions led to an imperial crisis, but civilian construction initially continued. After 250 AD, an economic decline set in, followed by relative stabilization around 269 AD. After Dacia was abandoned in 271 AD, Oescus became part of the province of Dacia ripensis, and the city area was expanded. In 328 AD, a Danube bridge connecting Oescus with Sucidava was inaugurated, increasing the city's importance. Archaeological findings suggest destruction during the Gothic invasion of 376–378 AD and the Huns' invasion. Justinian I presumably renewed the fortifications. The Roman city likely fell with the invasions of the Avars and Slavs around 586 AD. From the 10th to the 14th century, a Bulgarian settlement existed within the ruins.

The ancient city of Colonia Ulpia Oescus is located in Gigen, in the Guljanzi district, in the Pleven region of Bulgaria, at an elevation of approximately 22 m above sea level.

The remains of the ancient city can be visited today, offering insight into its former grandeur and significance.

• Nikopol Fortress (Fortress), approx. 34.3 km away
• Roman Castellum Storgosia (Ancient Buildings), approx. 38.8 km away
• Hisarya Fortress (Fortress), approx. 67.8 km away
• Roman Castellum Novae (Ancient Buildings), approx. 75.6 km away