The Early Bulgarian medieval fortress near the village of Skala is situated on the eastern terrace of the dry valley Kanagiol (Dristra in the past).
The fortress guarded the ancient road that connected the ancient city with Martsianapol Durastorium in the Middle Ages. During the First Bulgarian Kingdom, Drustur linked the current city Pliska and Preslav Silistra Capitals.
Late ancient and medieval fortress called Gradiste is 0,9km south – east in a straight line from the center of Skala. The castle is located on solid rock. It is protected from the west and the east by rocky ridges and steep rocky slopes and dale to dale of Chesmen of Osen. To the south there are the furrows of rock with a height of 15 m which closes the access to Gradiste. It is a form extended north – south, with a length of 96 m. width of 20 m and an area of 1.8 acres. It occupies an uneven cliff-top terrace and south of it and Brazda rock with a height of 12 m fort separates into 2 parts, of which the North can defend itself. The link between the two parts of the city was probably made by the wooden stairs. City walls are visible in the western, northern and in the eastern part. City wall is built of hewn stone, cement mortar white and red. The city has an excellent visibility to the east, west and south. The northern wall was the most vulnerable and accessible, so at 7 m in front of it, a ditch is built. The trench has a length of 30 meters and there is a preserved depth of 2 m and a width of 3 meters. Gradiste main gate is on the north wall until you leave the area “Yurta” where there was a settlement. Addressing the fortress was from the west. At the top of the fortress was built a square building, made of mix mortar probably. The pottery discovered is Byzantine and medieval Bulgarian (XI-XIV century). The fortress was defending and guarding the so-called “Road Peritski” and village population and the “Yurta” area.
The archaeological studies were published in the book “Skala – X-XI century fortress”, edition Bulgarian Academy of Sciences.