At a distance of 180 km from the Serbian-Romanian border, this fortress is one of the most important monuments in the Bulgarian state and one of the monuments that is still almost perfectly preserved. This fort was in the period of the Roman Empire's rule in the region, and the huge rock formations in the vicinity of the fort helped to add greater protection at that time, as some of these rocks reached a height of 70 meters! The fortress has been modified over the ages, as the Bulgarian ruler added to it and expanded it in the fourteenth century, and during the Ottoman rule it was changed significantly, but it was returned to its European character in the nineteenth century.