The Roman settlement of Transmariska arose in 40-50 AD. Until the end of the 3rd century, it was a permanent military post on the Danube Limes. In connection with the grandiose construction activity and military reorganization of the Danube Limes, Transmariska was visited by Emperor Diocletian in 294. On his instructions, the construction of the late antique castel began.

The construction of the fortress was completed in 299, when Diocletian came to the city for the second time. During his visit, an inscription was placed in which the fortress was called “praesidium”. The castel was one of the four largest military centers on the limes of the province of Second Moesia. Later, in the 5th and 6th centuries, Transmariska was an episcopal center.

The ancient castel “Transmariska” was declared a cultural monument of national importance in 1968.