Ancient Roman fortress Sostra located near the village of Lomets, 16 km from the town of Troyan. It is a settlement with a fortified military camp, built next to the road, which is of great importance to the Roman Empire. The road had a large extent: it begins at the Danube River and ends at the village Gigen (ancient city Ulpia Eskus), it was necessary to protect. Fortress Sostra located on the northern slopes of Stara Planina Mountain, just 100 meters from the path of Lovech - Troyan, to have survived very well, because, despite its advantageous location, during the invasion of the Huns (V c.) It was already inhabited.

It is interesting that in the territory there are fragments of three fortresses. Construction of the first buildings began around the year 147 by order of Emperor Antoninus Pius. However, in 249, the castle and the nearby military settlement suffered greatly as a result of the attack is ready. We know that five years later, the Emperor Gallienus ordered to restore the fort. The construction took three decades. The newly erected fortress wall (called the Eastern wall) reaches a height of 10 meters. Ruins of this wall survived. In the IV century as a result of yet another invasion ready Sostra was again destroyed. A century later, there was formed a peace settlement and the fortress finally lost its military character.

On the territory of the joke so far carried out excavation. In summer it is located archaeological youth camp. Already found many objects of culture and life of inhabitants of ancient fortresses: silver and bronze coins, weapons, armor, items, etc. of pagan worship.

After so many years of ancient Roman fortress Sostra is still not fully understood and interesting historical monument of Bulgaria.