Legionary fortress Sostra is located near the village of lomets, 16 km from the town of Troyan. It is a village with a fortified military camp, built near the road, is of great significance for the Roman Empire. The road had great length: he started at the Danube river and ended at the village of Hygiene (ancient town of Ulpia Escus), it was necessary to guard. Fortress Sostra, located on the Northern slopes of Stara Planina mountain, just 100 m from the path Lovech - Troyan to our time are still very well preserved because, despite its favorable location, in the years of the Huns (fifth century) it was already inhabited.

Interestingly, there are fragments of three fortresses. The construction of the first building began about 147, on the orders of the Emperor Antoninus Pius. However, in 249 the castle and a nearby military settlement was badly damaged in the attack ready. It is known that five years later the Emperor Gallienus ordered to restore strengthening. The construction took three decades. Newly constructed wall (called the East wall) will reach a height of 10 meters. The ruins of this wall has been preserved to our days. In the fourth century as a result of yet another invasion is ready Sostra was again destroyed. A century later it formed a peace settlement and the fortress lost its military character.

On-site Quipped still conducting excavations. In the summer there are archaeological youth camp. Already found a lot of objects of culture and life of the inhabitants of ancient fortresses: silver and bronze coins, weapons, armor, objects of pagan worship, etc.

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