Name:The castle of Iatrus bears the name of the Antiquity name of the river Iantra - Iatrus (Hdt., IV, 49 – ’Aθρυς; Plin., NH, III, 149 – Ieterus). The name has Thracian origin and is translated as "fast, turbulent".

Written sources:The earliest mention of the fort under the name of Latro (Latro) is found in Tabula Peutingeriana. From the "List of Offices" we learn that Laturs (Latius) has been under the military command of the Dux of the Province of Second Moesia and is a camp of a detachment of equestrian shield-bearers (NotitiaDignitatum, XL, 8, 13). In the treatise "On the Buildings" (De aedificiis) Procopius of Caesarea states that Emperor Justinian I "… with a new construction restored also the violated parts of the so-called frourion (fort) Yatron (’Ιατρων)". Describing the campaign of Peter, brother of Emperor Mauricius (582-602) against Avars and Slavs, in his work "History" Theophylact Simocatta notes Yatron as a town (τήν ’Ιατρόντήν πόλιν). The last mention of Iatrus, in the form of Latron (Latron) is discovered in the Anonymous Ravenna Cosmography, written in the early 8th century.

Location:The castle of Iatrus is located 40 km to the west from Rousse, immediately to the west of the village of Krivina, on a not very large hill that rises on the right bank of the river Iantra, at its mouth. The northern and western parts of the castle are destroyed by the waters of Iantra and Danube. The preserved area is around 2.5 ha.

History of the research: K. Skorpil is the first to identify the remains at the village of Krivina with the castle of Iatrus, basing on the distances marked in the Roman road maps (itineraries).At the end of the 19th century he made a short description of the site, accompanied with an eye-made plan. Later on, during an investigation of the lower region of the river Iantra, St, Stefanov gave information for the castle and the finds that originated from it. In 1958 joint Bulgarian-German excavations started as part of the implementation of a project for cooperative work between the then Institute of Archaeology at the Academy of Science of the German Democratic Republic (from 1970 Central Institute for Old History and Archaeology at the Academy of Science of the GDR) and the Archaeological Institute with Museum at the Bulgarian Academy of Science. In 1992 the direction of the German side was taken by the Rome-German Commission of the German Archaeological Institute.

Chronology:The chronology of the castle is presented overall in six volumes of the IATRUS-KRIVINA series. According to it the construction period “A” falls within the chronological frames of 310/320-350 AD. The “B/C” period covers the third quarter of the 4th century to the second quarter of the 5th century. The “D1” period existed during the reign of Emperor Anastasius I to the second decade of the 6th century, and the subsequent “D2” refers to the period of Justinian I up to the final destruction of the castle at the end of the 6th or the beginning of the 7th century.

The presented chronology of the castle is arguable. On the basis of his research in site XLIV, L. Vagalinski offers another chronology. He establishes a new period that immediately precedes the settlement period “A” and is thus called “-A” (up to this moment the materials from the 2nd-3rd century were interpreted as spolia). The “-A” period is represented within the borders of the XLIV site by two waste pits, two premises and a street surface. Each of the two premises has two burned floor levels. The first one – between 280 and 291/292, and the second one – built and fired after 292. The “A” period is dated before 347/348, and its beginning stands close to the time after the final of the second phase of “-A”. The beginning of the “B” period is after 347. Two phases are distinguished – “B1” and “B2”. Namely, during the first phase is the most intensive construction activity, and the architecture plan of “B1” is the backbone of the planning for the subsequent periods. Phase “B1” is destroyed by fire in the third quarter of the 4th century, after 367, and the most probable invaders are the Goths and their allies. During phase “B2” the manner of construction is the same as during the previous phase, a large number of spolia has been used. The end of “B2” is caused by a massive fire, dated after 402 or 408, and the probable attackers have been the Huns of the Union of Uldis. The “C” settlement period of the castle began with leveling of the destructions of the previous period. The technique of construction is different – crashed stone with clay joint, the use of adobe. Period “C” ends with the strongest fire in the history of the castle, testified along the whole of its territory, and according to the numismatic data the time of attack is after 425 during some of the Hunnic raids of the second quarter of the 5th century.

According to the chronology, included in the IATRUS-KRIVINA series, the “D1” period indicates the restoration of the castle during the reign of Anastasius around 500. It follows from here that between the periods “C” and “D1” there are at least 50 years of hiatus. Such, however, lacks at the stratigraphy of site XLIV, and “D1” lies immediately over the massive fire from the “C” period.According to L. Vagalinski the dating for the beginning of “D1” around 500 is influenced more by the historical events than from the real stratigraphic picture. The end of the period is after 518. According to the official chronology of the site the next period “D2” covers the time from the second quarter of the 6th century to the final destruction of the castle at the end of the 6th or the beginning of the 7th century. Theophylact Simocattamentions Iatrus in relation to the events of 600, but this could be an indication of a toponym, and not its actual existence at the time, moreover the latest coin known from the castle is minted in 577/578. Probably at that time or soon after that the castle has been destroyed and the attack is registered over the entire castle territory.

Revealed structures and finds: Given the configuration of the terrain, the fortification has an irregular elongated shape with approximate size of 300 x 100 m. At the preserved eastern and southern parts of the fortification, the wall has been examined by drillings. The substructure (foundations) begins at a depth of 1.5 m from the terrain level and its width is 4.00 – 4.10 m, made of crashed stones and white mortar. In the separate sections the width of the superstructure varies from 3.00 to 3.50 m. It is constructed, at least the plinth level, by large quadrae according to the "Binder-Laufer" system (rowing in length and crosswise placed blocks). The emplecton is of crashed stones and white mortar. Eleven towers have been localized – three corner ones with the shape of a horseshoe (№№ 1, 7, 11) and eight median, of which seven with U-shaped (№№ 2, 3, 5, 6, 8, 9, 10) and one with a rectangular shape (№ 4). Out of them, entirely examined are the towers with numbers 1, 2, 4. Tower № 1 has an external length of 9.60 m and a maximum width of 10.50 m. The internal size are respectively 8.10 and 5.00 m. The entrance is 2.07 m wide, and its length is 3.50 m, in similarity to the curtain. Tower № 2 has external size of 9.84 x 9.00 m and a thickness of the walls of 3.00 m. The core of the fortification system of the castle is the rectangular tower № 4, which with its imposing parameters (30.45 x 15.25 m)is without an analogue among the monuments of the Roman fortification art in the territory of Bulgaria. It is protruding 9.50 m outside the curtain and 2.10 m to the inside of the castle. In the middle of the northern wall is the entrance with 1.90 m width. There are four pillars with size of 2.26 x 1.65 m inside of the tower. The distance between the separate towers is relatively small and varies between 15.20 and 16.00 m. The access of the castle has been implemented through a tower-gate (with size 9.20 x 9.50 m), made in a slump of the eastern fortification wall. For its more effective defense, the gate is flanked by two U-shaped towers with numbers 8 and 9 that are standing correspondingly on 12.50 and 20 m away from it.

The planning of the castle is determined by the street network. The main street that has functioned during the entire existence of the castle and with different construction periods being marked on it, is via praetoria. It starts from the single gate of the castle, the eastern gate (porta praetoria). At several meters away from it, the street makes a curve at an obtuse angle in direction from southeast to northwest and directs towards the Principia of the castle, where it ends up. Via praetoria separates the built-up territory of Iatrus in two parts: a smaller northern one and a larger southern one. Its length is 115 m, and its width in the western end during the “A” period is from 7.10-7.20 m. On both sides, along its entire longitude, it is flanked by a colonnade in Roman-Doric style with a width of 3 m. The two porticos formed this way, begin at 7 m to the west of the gate. The main street is preserved better in its western end. Its surface consists of the following elements: a clay layer at the bottom, a pad of irregular stones with clay, and a clay layer with gravel and fragments of construction and everyday pottery at the top. At 17 m to the north of via praetoria is located the first parallel small street, which should lead its beginning from tower № 10. Another small street with a width of 1.20-1.90 m, documented in sites ХХХІІ, ХХХІІІ, ХХХІV, is located at 32 m from the yard of the Principia. It has a north-south direction, and in southern direction it probably reached the large rectangular tower № 4. To the west of site XXX is presumed the existence of another small street directed eventually towards tower № 5. To the west of the Principia is via quintana, which during the “A” period has been directed towards tower № 2. On the inner side, along the fortification wall, is located via sagularis. During the “B/C” period via praetoria made a narrowing between sites ХХVІІ, 1 and ХХХІІ, 1. Together with the erection of horreum VII disappeared the old intervallum along the southwestern section of the fortification wall. Similar events are observed in the area of the gate, too. Other changes take place as well, because some of the streets received a new orientation or were even moved (between sites ХХІХ and ХХХ). Only on a few places can be distinguished the levels and surface between construction periods “A” and “B/C”. The new surface of the main street from the second period is determined at via quintana and the small street at site ХХХІІ. At the end of the second construction period via praetoria is renewed again, the street level is lifted a little bit, and the surface is of stones, clay and fragments of brick. During the “D1” and “D2” periods the main street preserved its functions and layout.

The core of the architecture scheme of the castle is the Principia. It is not located in the central part of the castle, but is shifted in western direction. It consists of a peristyle yard, a rectangular hall and a semi-round apse (exedra). Its length is 24.80 m (east-west), and its width – 14.80 m. The last one corresponds to the width of via praetoria and its belonging lateral porticos. The peristyle yard has a size of 13.40 x 10.47 m. It has four Doric pillars on each of its long sides, and three on each of the short ones, or a total of ten pillars. Four covered porticos are formed with a floor covered with white plaster. The yard itself is covered with crashed bricks. The entrance to the peristyle yard has been implemented from via paetoria through a 3 m wide entrance in the eastern wall. Three entrances led from the yard to the hall. A stone threshold with two steps is preserved at the middle entrance. On one of them are distinguishable nests, which indicate that the door has been two-folding. The level of the plaster floor of the hall is 0.30 m lower than that of the peristyle yard. The thresholds of the other entrances have been removed, but their beds are visible. To the west of the hall is the exedra with an inner radius of 3.60 m, shifted from the longitudinal axis of the building to the north with 0.30 m. It represents a platform that is lifted above the floor level of the hall with 0.60 m. The threshold consists of quadrae with size of 0.60 x 0.55/0.65 m. Lower blocks for steps are placed from its facial side. On the upside along the length of the threshold is carved a channel for a wooden baffler, probably with a door in the middle for the apse premise. The Principia is constructed of limestone quadrae jointed with white mortar. The thickness of the outer walls of the peristyle yard is 0.60 m, and of the hall and the apse – 0.90 m. The only finds of the Principia are a base and a sacrificial altar. The first one lies on a pedestal next to the western wall of the hall in its northwestern corner. The sacrificial altar is found over the brick floor of the apse.        According to its researchers, the Principia of Iatrus functioned as such during the “A” period. To the same time should be referred the presence here of one cuneus equitum scutariorum (detachment of equestrian shield-bearers), mentioned in the "List of Offices", or., 40. L. Vagalinski contravenes to this, stating that the construction of the Principia afundamentis should be placed within the chronological frames of construction period “B”, as well as the station here of the mentioned military unit. Given the almost identical plan-composition scheme and parameters of the Principia with the one of the castle Sexaginta Prista, which is surely dated from the first quarter of the 4th century, the synchronicity of the two causes no doubt.

To the south of the Principia is located a construction complex, to which belong a building that resembles a hall (site XVII), a square with a base for a honorary pillar, and to the east there is a lateral wing with internal yard (site XXXVI), as well as a small bath. The complex is interpreted, on the basis of its location, as a praetorium. Behind the portico, at the northern side of via praetoria are located tabernae and premises with other functions, in two rows – with size of 6 x 6 m (site XXVIII). The three western premises may have had a functional connection with the Principia (site XXXV). To the west of it there is a quarter, which does not touch the main street and thus looks a bit isolated. The working hypothesis is that the barracks have been located here (site X), the officers’ residences and the administrative premises. The destruction of the architecture of settlement period “A” can be determined with a high degree of certainty. Before the beginning of construction works during the “B/C” period, a large part of the existing buildings have been removed, with even the lower blocks of the substructure of the walls being affected. The structure of the buildings shows that in relation to the previous, the “B/C” period has a significantly changed character. After the end of period “A”, the Principia no longer executed the functions of a governing center in the castle, a function that has been transferred from the early phase of period “B/C” to the first basilica of Iatrus (basilica B), erected on the highest place of the surrounded area. The basilica B is a three-nave, with one apse, of the Hellenistic type. It consists of a narthex with size of 10.00 x 9.20 m. Two rows of three constructed pillars of each are separating the naos in three naves. The foundations, 0.60 m wide, are constructed of crashed stones, jointed with mortar mixed with crashed brick. Its modest plan and shortened proportions indicates the early phase of the development of this architecture type, which corresponds to the stratigraphic results of the excavations. On the basis of the numismatic data, its construction can be referred to the reign of Emperor Constantius II, i.e. around the middle or the beginning of the third quarter of the 4th century. Basilica B has been used up to the end of the first quarter of 5th century, when it has been destroyed by fire. Soon after that basilica C was constructed. It is a three-nave, with one apse and outer size of 22.20 m (together with the apse) and a width of 12.20 m. In the middle of the narthex there is an entrance, 2.20 m wide. There is also an entrance on the northern wall, in proximity to the northeastern corner. The naos is separated by two rows of pillars, standing over a solid stylobate. The floor is covered with bricks. The bases, 2 m deep, are made of crashed stones, jointed with white mortar, and the superstructure is in belts of stones and bricks, probably four rows. The basilica has a baptistery, located in the neighbouring site XV, as well as a premise with mensa sacra. The entrance to this additional building was from the northern isle of basilica C. Built in the 20’s of the 5th century, the building suffered serious construction changes (additional premises to the internal side of the narthex and enlargement of the entrance to the it), but preserved its functions. It was destroyed in the 40’s of the 5th century. During the “B/C” period other changes took place as well. Together with the building of the horreum VІІ, located around the southwestern fortification wall, which had a solid construction and imposing size (length of 61.50 m and a width of 16.50 m), during the early phase of the “B/C” period another storage building is constructed – horreum І, to the west of the former Principia. In difference to horreum VІІ, which also executed a function to the fortification system, because it strengthened the internal section of the wall, long around 45 m (where apparently no tower has been built on the outside), horreum І had a clearly economic functions. The entrance to it is located from its eastern side, i.e. it is directed towards the center of the castle, and not towards the river, which can serve as an indirect proof against a presumable gate on the side of the river Iantra. The two horrea in Iatrus suffered a great fire during the first quarter of the 5th century, when basilica B was also destroyed. After their demolition, they were not restored in their previous shape and functions, but next to the survived outer walls were erected several small residential and crafts buildings, made of bricks. In site ХVІ is discovered a small bath, attached to the outer wall of the porch of the former Principia. Not long after that, but within this period, the bath received other functions, the median wall and the hypocaust were removed, through which the building was transformed into a single premise. Besides the two horrea, another building can be identified as an economic one – the building in site ХVІІІ. In the largest premises of this site are found ten elevated work grounds and a large number of mills, which leads to its interpretation as a mill. In the neighbouring site XIX are discovered several similar grounds, and the rest of the finds show that in the building has been processed metal and metal objects. The larger part of the buildings that existed during the “B/C” period are residential-economic buildings with various plans. These are usually several premises, grouped not very strictly around a small yard. On the basis of these buildings can clearly be distinguished the gradual change of the camp architecture from period “A” towards an architecture that satisfies civic and farming needs during the “B/C” period. Due to the presence of the large warehouses and a mill, it can be presumed that these were facilities, although only partially, for the remaining central directed supply of the food needs of the residents of the castle. These structure changes can be related to the assumption that after the withdrawal of the military contingent at the end of period “A”, Gothic foederati have been settled here with the task of assuring the military security in this section of the Limes. Several small finds are also in favour of this hypothesis.

The end of period “B/C” is caused by a large fire that has destroyed everything within the castle area. According to the coin hoards, this destruction can be dated within the second quarter of the 5th century and mainly in the 40’s of the century, and thuss to be related to the invasion of the Huns.

After the castle was destroyed and abandoned at the end of period “B/C”, for a long time there was no organized castle life. There is a lack of data for the presence of permanent military units here. During the reign of Emperor Anastasius (491 – 518) the Goths withdrew from the Province of Moesia Secunda, after which began the overall restoration and reorganization of the border defense. This led to the beginning of the “D1” construction period of the castle of Iatrus. It was resettled again, but more scarcely and not over the whole of its territory. Over the remains of the old destroyed buildings were erected new ones, but according to the construction techniques and the use of materials, they deferred to those of the previous periods. The only building that stands out during the period (but with unclear functions) is located in site XXXIII – to the east of the first cross street on the northern side of via praetoria. It is distinguished by a premise that resembles a hall, with a colonnade in front of it. The settlement during period “D1” is not essentially showing a different structure from the one of the “B/C” period, except for the fact that it is significantly scarcely built-up. Towards the end of the period the entire castle was destroyed by fire, which according to the coin hoards happened around the 20’s of the 6th century. It is not clear when exactly was the camp from the time of Anastasius destroyed, as well as the precise dating for the restoration phase during the reign of Emperor Justinian, but stratigraphically the two periods are clearly separated, becauset he buildings from the time of Justinian have an entirely different character. During the time of period “D2” via praetoria passed through a poorly built-up area. Only the former bath – site XXVI, as well as the warehouse building in site XXXI, to the north of the former Principia, were used again. Apparently, in Iatrus during the “D2” period there few newly erected stone buildings. Only one of them has been studied – site XXI, located above the former Principia. Due to the furnace, constructed in it, it is considered to be an economic one. The larger part of the area of the castle consists of small huts, dug into the ground, sometimes rising a little above the terrain level, made of adobe. Although not densely, they were filling the entire area of the castle. In this settlement of huts and several stone buildings, basilica D was distinguishable, erected on the site of the basilicas of the “B/C” period. It covers the plan of the previous two, but in much larger size: length of 30.30 m (together with the apse) and a width of 16.20 m. Its foundations were of roughly cut stone blocks, jointed with white mortar. A massive stylobate, 1 m wide, over which were lying pillars of columns, separates the naos in three isles. The outer walls are with thickness of 1.25 m, and the floor is covered with bricks. A baptisterium was built additionally at the southeastern corner, with size of 5.80 x 4.10 m, preserved only in its substructure, as well as the basilica itself. Its construction refers to the first decades of the 6th century. 

In the course of four decades of archaeological studies, thousands of finds are unearthed in Iatrus. Among them there are various architectural details and decorations, altars and votive material, items of the bronze and stone plastics, hundreds of adornment and elements of the costume, typical for the different periods of fort's existence, household items. Specifically numerous are the collective and identical coin hoards, among which there are three that contain golden solids of the Late Antiquity and the Early Medieval period of the fort.