Thracian and medieval fortress Kartal kale translated from Turkish as the “Eagle’s Fortress” is located 2.9 km southeast in a straight line from the center of the village Ruyno. The castle is located on one edge, rising above in the deep valley of the dry  Srebarnitsa river. The access to edge is possible only through a narrow elongated space, bordered by cliffs. The castle has an irregular shape, dictated by the shape of the terrain. Its area is of about 50 acres. The Western Wall was the best fortified, being located on an inclined surface. There are visible traces of the five towers, the water ditch and a tree. The southern wall had also three towers. The wall was probably placed at the entrance leading to a river. The north wall was thin and not very high because of the abrupt stone wall. The fortress wall was built close to the edge of the terrace. It has 2.8 m width and 2 m height. The wall is built directly on the ground without any foundation.  The presence of materials from the fifth century BC is an evidence that the place was inhabited by Thracians. There are numerous indicators suggesting the Thracian settlement. There are two early medieval fortresses in the village – Kartal Kale and Ayazmoto, located just 1.5 km distance from each other. This is an unprecedented case in the construction of the First Bulgarian Kingdom fortification. The two cities guarded the road from Preslav – Pliska to the Danube.