The ruins of the Late Roman and Early Byzantine fortress and early medieval Bulgar settlement Iatrus (which is also the ancient name of the Yantra River in Central North Bulgaria) are located near the town of Krivina, Tsenovo Municipality, Ruse District. It was an important Roman fort along the so called Limes Moesiae – the system of frontier fortifications of the Roman Empire along the Lower Danube designed to thwart barbarian invasions from the north in the Late Antiquity. Iatrus is also believed to be the name of a little known deity from the Ancient Thracian mythology.
The Roman fortress of Iatrus existed from the 4th century AD until the 6th century AD when it was destroyed in the barbarian invasions of the Avars, Slavs, and Ancient Bulgars. The Roman fort had a territory of about 30 decares (app. 7.5 acres), and was fortified with a stone wall with fortress towers. It became the site of an Ancient Bulgar settlement during the time of the First Bulgarian Empire (632/680-1018 AD) which existed from the 8th until the 11th century.
In the 2nd-3rd century AD, Iatrus was initially a Roman road station and unfortified settlement, as indicated by Roman road maps such as the 4th century Tabula Peutingeriana (the Peutinger Map showing cursus publicus, the road network in the Roman Empire, covering Europe, North Africa and parts of Asia) which noted that it was located 9 Roman miles away from Novae (today’s Svishtov) and 16 Roman miles away from Trimamium (today’s town of Mechka).
In the first quarter of the 4th century, during the reign of Emperor Constantine I the Great (r. 306-337 AD), the Romans built a fortified military camp (castra) at Iatrus, on the right bank of the Yantra River, close to where it flows into the Danube, on a steep plateau with natural defenses.
The fortress wall of Iatrus was up to 3.5 meters wide, and up to 10 meters tall. The heptagonal fortress had 12 fortress towers, some of them U-shaped; two towers defended its only gate. Iatrus also had one huge rectangular tower which was 30.5 meters long, and 15.3 meters wide, and was the largest known Roman Era tower on the territory of today’s Bulgaria.
The Iatrus Fortress survived in its original form until the 370s, possibly until after the Battle of Adrianople in 378 AD in which the Goths routed the forces of (Eastern) Roman Emperor Valens who was also killed in the battle.
Not unlike the other Roman military camps in today’s North Bulgaria, after the barbarian invasions in the late 4th century, Iatrus was transformed into a fortified civilian settlement. Its military buildings were abandoned after they had been destroyed in a fire. The settlement was probably inhabited by Gothic foederati subsisting on agriculture and crafts. Its residents still participated in the defense of the Lower Danube frontier of the Eastern Roman Empire (Byzantium). Iatrus was raided during the barbarian invasions of the Huns in the middle of the 5th century AD. It was rebuilt briefly during the reign of Emperor Anastasius I Dicorus (r. 491-518 AD) but was once again burned down by invaders, possibly Ancient Bulgars. The settlement was revived under Emperor Justinian I the Great (r. 527-565 AD), and was ultimately destroyed by the Avars and Slavs at the end of the 6th century AD.
Several decades after the Roman and Byzantine fortress and settlement Iatrus had been completely abandoned, it was settled and fortified anew by the Ancient Bulgars; after the center of the First Bulgarian Empire was transferred south of the Danube ca. 680 AD, Iatrus became a major Bulgar settlement with a military garrison. In the 9th-10th century, the Bulgar settlement featured large residential buildings, possibly with two-floors. In one of the these buildings, the archaeologists have found 45 Byzantine gold coins, a discovery seen as indicating of the high economic status of the settlement.
The Ancient Bulgar settlement at Iatrus was destroyed in a huge fire ca. 970. It is believed that, not unlike a large number of other strongholds of the First Bulgarian Empire, it was burned down by Knyaz Svietoslav I Igorevich, ruler of Kievan Rus (r. 945-972 AD) who invaded the First Bulgarian Empire in 968-971 AD). Individual artifacts indicate that in 11th century the site was briefly settled by Pechenegs.
The site of the ruins of Iatrus was first identified by Czech-Bulgarian archaeologist Karel Skorpil, the father of modern-day Bulgarian archaeology. The site was first excavated in 1958-1962, and then again throughout the 1970s, by archaeologists from Bulgaria and the German Democratic Republic (i.e. the former East Germany). In 1992-2002, the excavations were conducted by the National Institute and Museum of Archaeology in Sofia, the Ruse Regional Museum of History, and the German Archaeological Institute (Deutsches Archäologisches Institut).
The Bulgarian and German archaeologists have discovered the eastern and only gate of the Iatrus Fortress, two Early Christian basilicas, a number of private and public buildings, Byzantine gold coins from the 10th century, and various artifacts.