The fortress is located on the peak. Hisarlaka, has the shape of an irregular trapezoid and encloses an area of about 8000 square meters. A lot of the 2.5 m. thick walls are preserved, in places they rise up to 8-10 m. in height. Three of the entrances are also preserved, and in it’s eastern part there is the 12-meter water well. Due to the typical construction, archaeologists have determined that the fortress was built in the late sixth century by the Romans, in order to protect from invasion from the north by Barbarians, and probably the fortress lasted until the end of the Second Bulgarian Kingdom. Kipilovo fortress is situated 3 km southeast of the village of Kipilovo, municipality of Kotel. Kipilovo is located 17 km west of the municipal center. The thickness of the walls of all of the three fortresses is 2-3 meters. In this respect the citadel near Kipilovo is the most preserved. To the northeast, the wall has been reinforced with 12 counterparts, which doubled the strength of the building and assumed the inclining forces that appeared in the structure due to the uneven terrain. The stone wall of the fortress is made up of emplekton and tufell, it was distributed in antiquity in the Roman provinces of Lower Moesia (present-day northern Bulgaria), coastal Dakia (now Vlahshko), Dobrudja and the Black Sea coastal region. The emplekton of the wall is a dense mass of gravel and unfinished stone, which is bonded with white mortar. The composition of this building material also includes ceramic pieces. All this is done for strength and durability. Тhe outside frontal parts are lined with tufts only – processed stone blocks.Of the three fortresses that guard the passage “Iron gates” – the most preserved are the gates of Kipilovo fortress. Unfortunately, the ruins of the defense gates at Bebrovo and Kostel have not yet been found. The gates themselves are an important element of the fortification system of each citadel. Usually they were built in the most inaccessible places. Three types of gates – passage, polygonal and triangular – are known from antiquity and the Middle Ages.
The main fortress door of the Kipilovo’s castle is of gate type, the second floor of which serves as a tower. It consists of two doors located in the southeastern part of the tower. The outer door is located at an angle to the road and the inner gate. The inner door itself represents a two-row brick arch. This tower has a trapezoidal shape. Another very important part of the defense of any fortress is the so-called “Poterna” (small entrances to the fortress walls).There were 11 poternas in the walls of Kipilovo fortress, of which only two had survived. As the fortress gates and poternas were constructed in inaccessible places. Unlike the late Roman fortress facilities, the poternas near the village of Kipilovo have small dimensions. In this fortress they are located in the most inaccessible places, which doubles the defense of the fortress walls, and hence – of the whole fortress. This shows that the fortress has played an important role in the defense of the passage. In Kipilovo, apart from the poternas, some of the towers are also preserved. They are a mandatory element in any defense facility. This principle has not changed either in antiquity nor in the Middle Ages. There are five towers at the edge of the citadel, which are located at the corners and at the front of the wall. Multi layered in structure, they are internal and external. The Tower is preserved at a height of more than 6 meters (the highest surviving ruins). The four layers of blocks are noticeable there. This facility had two floors. The second floor is visible from the inside. A square tower rises in the southwest corner of the fortress on the edge of the rock step. Its remains are preserved at a considerable height. The tower has a protruding southeast ridge that goes down the steep slope. The construction of this type of towers is widespread during the first centuries of the New Age.Their task is to reduce the devastating effect of siege machines. The protruding edges of the tower create a ricochet effect. There is a large outer rectangular tower in the central section of the northern wall. Different levels of the drainage apertures of the outer facade of the tower suggest for its multi-storey. In the area of the fortress there are two more towers – one is pentagonal and is located on the south wall and the other is a triangular tower. Fortress however, was tightly built. Most buildings are in its narrow northwest sector. There dominates a rectangular room with thick walls. The room is located parallel to the northern fortress wall. This corridor had served for maneuvering of the defenders. According to the excavations, it had three doors and two cone-like battlements.
Perhaps the building served as a guardhouse and as a “citadel” – a last resort of protection. Kipilovo Kale is situated 3 km southeast of the village of Kipilovo, Kotel Municipality. The village of Kipilovo is 17 km west of the municipal center.