Kula is a town in northwestern Bulgaria, Vidin is separated by 35 miles. The ruins of the fortress of Castra Martis late antique period are located right in the Central part of the Kula.

The fortress is a monument of architectural and building skills, which was published in 1965 in one of the rooms of the newspaper "State Gazette". The fortress is inextricably links the modern Bulgaria with Bulgaria ancient, when these territories belonged to the Romans and then the Byzantines. Not far from the remnants of the stronghold scientists and archaeologists was made up of exposure, which is before the tourists and townspeople finds discovered during the study of the structure.

Archaeological excavations have shown that before on the same slope until the Roman fortifications were tiny settlement of the Thracians belonging to the first Millennium BC

The construction of Castra Martis was carried out in order to protect strategically important to the Romans the way to Singidunum (modern Belgrade) from Bononia (now – Vidin). The fortress itself is divided into two parts: quadrilogy – strengthening small square shape, and Castel – part of the fortress from the South. It is noteworthy that these two parts Castra Martis were built in different time intervals.

At the end of IV century, the fortress was destroyed during the invasions, but the greatest destruction was caused by the raids of the Huns at the beginning of the fifth century.

The Museum collection consists of a variety of tools – from farmers and ranchers to masons and builders. Also presents devices used military Castra Martis in the subsidiary. The illustrated life of the inhabitants of clay lamps and vessels of various forms, covered mainly brown and green glaze. In addition, part of the exhibition are coins and bronze fibulae of the IV-V centuries. Reminders about military events of the ancient period are the arrowheads and spears.

At the fortress Castra Martis equipped with a viewing platform, the view which opens directly on the main street of the city of Kula. At night the castle is illuminated in a special way.