Dimum dates from the 1st century to the 7th century throughout the Roman period in Bulgaria. It is one of the major urban centers of the Danube and it is the last, northernmost customs station, which is why it has been rebuilt five times during this period. Dimum was declared a monument of national importance in 1968. Over the years, the Municipality of Belene has carried out restoration and restoration of part of the ancient Roman fortress “Dimum” in its form from the IV century. Parts of the camp can be seen north of the Vasil Levski school. The ceramic materials from Dimum testify that its terrain was inhabited by Slavic Bulgarians in the IX-X century. Medieval Byzantine and Bulgarian coins mark its presence in the X-XIV century, and archaeological finds from the last cultural layer show that it has existed without interruption to this day, thanks to its last settlers – the Paulicians. Over the years, Turks, Vlachs and Orthodox have settled here. To this day, they have survived as religious communities with their way of life, culture and live in peaceful coexistence and understanding.
Dimum was the northeasternmost point of the province. During the expansion of the Roman Empire to the east, the castle was bordered by the so-called Illyrian and Thracian customs, which were united at the end of the 2nd century. In Dimum, at the beginning of the 2nd to the end of the 3rd century, a military cavalry unit was stationed, which probably built the fortress itself.

Dimum is the earliest customs. Here was the border of the Thracian kingdom and the Roman province of Moesia during the time of the first Roman emperor Octavian Augustus. Dimum was declared a monument of national importance in 1968. Drilling of the site began in 1989, when part of the fortification system of the castle was studied and a preserved area of ​​about 60 meters was discovered.
During the 1990 campaign, the southern tower of the western fortress gate – the Pretoria Gate – was opened.
After a break of 17 years – in 2007 – regular excavations began again. In just one month, about 56 items were found, including a bronze statuette of the goddess Demeter (Isis), a bronze belt buckle, earrings, appliques, glass bracelets, household items and 20 copper coins.