The Roman settlement Transmariska is established in 40-50 AC. It is a permanent military station in Danube region till the end of the 3rd century. In connection to the great construction activities and military reorganization of the Danube district, Transmariska is visited by Emperor Deokletian in 294. He ordered the building of the castle. The castle was finished in 299, when Deokletian visited the city for the second time.
The Roman and Byzantine castle, under the modern Tutrakan, is 65 acr. Some of the towers are square, including the restored tower №1, discovered during the archaeological excavations in 1995-1997. The tower has a postern on its western wall. The castle was restored and preserved in 2000- 2001. In the area between the streets “Kreposta” and “P.Beron” was discovered also the south wall of Transmariska with two battle towers – one horseshoe shaped and the other harp shaped. The wall is a significant archeological monument and an interesting tourist sight. Antique castle Transmariska was declared a cultural monument of national importance in 1968.