Basing on the latest research in the domain, the present paper is meant to update on the question of the Roman Empire domination north of the Danube, after Aurelian's withdrawal. In view of the desired updating, a fixed repertoire of the late Roman fortifications situated on the left bank of the big river has been drawn up; it is divided into two separate parts: the first one, corresponding to the end of the 3rd century and the beginning of the 5th while the second one corresponds to the end of the 5th and the 6th century. The repertoire also includes the fortifications of the Danube isles. The military quarters which interested these fortifications have not been included and will be analysed on a different occasion.
For the first period, the repertoire comprises a total of 31 fortifications presented in the geographical order from the west to the east as follows: Cenad, Pancevo, Constantia - ContraMargum (Kuvin), Sapaja, Banatska - Palanka, Vrsac, Tibiscum (Jupa), Pojejena, Moldova Veche, Gornea, ContraRegina, §vinița, Dubova, Dierna (Orsova), Praetorium (Mehadia), Ducepratum (Ada-Kaleh), Transdiana (The Banului Isle), Drobeta-Theodora, Puținei, Hinova, Tismana-Batoți, Izvorul Frumos, Ostrovul Mare, Izvoarele, Alba, Lucus/Lucum, Desa, Bistre?, Sucidava-Sykibida, Turris, Turnu-Mágurele, Dafne-Marisca, Pietroasele, Piua-Pietrii, Barboși, Aliobrix, Tyras.
13 of these are already mentioned in the literary and epigraphical sources: Constantia-Contra Margum, Tibiscum, Contra Regina, Dierna, Praetorium, Ducepratum, Transdiana, Drobeta-Theodora, Sucidava-Sykibida, Turris, Dafne, Aliobrix, Tyras, din care doar 7 au fost localizate pe teren în mod cert (Tibiscum, Dierna, Praetorium, Ducepratum, Transdiana, Drobeta-Theodora, Sucidava-Sykibida).
25 of the same have been identified with certainty, by archaeological digging or informative research: Pancevo, the Sapaja isle, Vrsac, Tibiscum, Pojejena, Gornea, §vini?a, Dierna, Praetorium, Transdiana, Drobeta-Theodora, Pu?inei, Hinova, Tismana-Bato?i, Izvorul Frumos, Ostrovul Mare, Izvoarele, Desa, Bistreț, Sucidava-Sykibida, Turnu-Mágurele, Pietroasele, Piua-Pietrii, Barboși, Aliobrix.
Four fortifications have been hypothetically identified, judging by the construction remains, the military stamps or the coin circulation in the late Roman age: Cenad, Banatska-Palanka, Moldova Veche, Dubova.
Two of these (Alba and Lucus) have been inferred (indirectly attested) by recourse to the literary sources.
Of the 25 fortifications identified with certainty, it could be noticed that in 5 cases the old castrae were used (Tibiscum, Pojejena, Praetorium, Drobeta-Theodora, Desa), the remaining twenty being new constructions.
From a strategical standpoint it can be noticed that the majority of the fortificatins have counterparts on the southern bank of the Danube: Pancevo-Singidunum, ContraMargum-Margum, Banatska Palanka- the Sapaja isle-Laederata, Pojejena-Pincum, Moldova Veche-Cuppae, Gornea-Novae, ContraRegina-Regina, §vini?a-Boljetin, Dubova-Hajducka Vodenica, Dierna-Transdierna, Ducepratum-Sip, Transdiana-Diana, Drobeta-Transdrobeta, Izvorul Frumos-Egeta, Ostrovul Mare-Mihailovac, Izvoarele-Aquae, Alba-Transalba, Lucus-Translucus, Desa-Ratiaria, Bistre?-Cebrus, Sucidava-Oescus, Turnu Mágurele-Asamum, Dafne-Transmarisca, Piua Pietrii-Carsium, Barboși-Dinogetia, Aliobrix-Noviodunum. Although it is undeniably true that the north-Danube fortifications regarded as a whole represent mere extensions in the Barbaricum zone of such constructions as the ones to the south of the big river,in whose absence they could not have existed at all, it is still provable that they represented the lower Danube limes in the late Roman age, together with the access roads for the troups and the earthworks (Lat.: valla). A good number of them are situated in the vicinity of some rivers' mouths: Pancevo- the Timiș river, Banatska Palanka and the Sapaja isle- on the Caraș and Nera rivers, Pojejena-the Radina river, Gornea- the Căunița river, Dubova- the Morilor stream, Dierna- the Cerna river, Drobeta-on the Topolnița river, Bistreț- on the Desnățui river, Turnu Măgurele- on the river Olt, Dafne- the Argeș river, Piua Pietrii- on the Ialomița, Barboși- on the Siret, Tyras- on the Dniestr. Under the circumstances, it is obvious that they also served for preventing the potential invasions along the valleys of these rivers.
It can be noticed that the corresponding fortifications of the Moesia Prima province and in part of the province Dacia Ripensis (up to Dorticum) are more frerquent than the ones of Oltenia and Muntenia. This could be explained by recourse to several factors: the state of the art in research in general , the existence of some foederati (the Goths), the resistance of the defence system east of Dorticum and the increased safety level of the naval transport on the Danube as compared to the one in the Iron Gates area, so much more vulnerable, the earthworks (valla) in the region of the Danube plain and the south of Moldavia.
The fortifications which are situated at greater distances from the Danube (at Cenad, Vrsac, Tibiscum, Praetorium, Puținei, Pietroasele), reflect extremely well a certain military and political situation existing in the former Dacia, namely the superiority of the Empire in respect to the barbarians, which had been the case ever since the time of Constantine the Great (324/332). Two of these fortifications, i.e. Praetorium and Puținei, seem to have been the outposts of Dierna and Drobeta, respectively, which denotes the exceptional importance of the latter.
In the present research stage it is not possible to confirm a Dacia restituta, as claimed by some archaeologists. As for the possibly reiterated take over by the Empire of certain territories to the north of the Danube, it is out of the question before the time of Constantine the Great.

The Typology, Forms and Constitutive Elements of the Fortifications
No exhaustive study of the fortification typology to the north of the Danube during the late Roman period can be undertaken in the current research stage, since the layout of all the fortifications is not known. Part of the known layouts ( those of Pancevo, Constantia-Contra Margum, Sapaja, Tibiscum, Pojejena, Gornea, Dierna, Praetorium, Ducepratum Transdiana, Drobeta, Puținei, Hinova, Tismana-Batoți, Izvorul Frumos, Izvoarele, Desa, Bistreț, Sucidava, Turnu-Mágurele, Pietroasele, Piua Pietrii, Barboși) come from Marsigli, and only a small number of these were thoroughly and scientifically drawn. The literary and epigraphical sources further complicate this situation in so far as they use different terms: castra, castella, praesidia, burgi, monopyrgia, while modern historiography has adopted the term quadriburgium to refer to the fortifications of the period from Diocletianus to Constantine the Great. Reviewing the existing information and considering the construction particularities, we assume that the following typology could be outlined:
I - the castra type fortifications are big forts, quadrangular in form, with or without corner towers protruding from the precinct. In this type are also included some old castrae refurbished in the 4th century (Tibiscum, Pojejena, Praetorium, Drobeta, Desa) with three out of their four gates blocked, as well as new constructions (Puținei, Tismana-Batoți, Izvorul Frumos, Izvoarele, Bistreț, Pietroasele, Piua Pietrii).
II - fortifications of the quadriburgium type: completely new constructions, approximately square in outline, small-sized, provided with square or round corner towers protruding from the precinct. The access to them was through a single gate generally situated on the southern side. This type includes the following fortifications: Pancevo, Sapaja, Gornea, Dierna, Ducepratum, Hinova.
III - triangular fortifications; they are new constructions with round corner towers protrunding from the walls. The earthworks of Constantia-ContraMargum and Transdiana belong here.
IV - irregularly polygonal fortifications large in size, with corner and median towers protruding from the precinct. The Sucidava fortification is of this kind. V -surveillance and signalling fortifications (i.e., towers); they are entirely new constructions as well, reduced in size, having no defence function. §vini?a, Turnu-Mágurele, Barboși and maybe Turris are to be included here.

The Construction or Reconstruction and Repair Phases
The following construction phases can be established, taking into consideration the fortifications on the southern bank of the big river:
1. Gallienus-Aurelian; although not recorded by the literary sources, this phase was archaeologically ascertained at Drobeta, where the old castrum was refurbished and at Sucidava, where the first military fortification (viz. the inside precinct wall) was erected .
2. The first tetrarchy (Diocletian's); the quadriburgium type fortifications erected near the Danube, rectangular in their layout and small-sized: Pancevo, Gornea, Dierna, Ducepratum, Hinova. It is similarly to this epoch that the following can be circumscribed: Banatska-Palanka(?), Pojejena, Transdiana, Tismana-Batoți(?), Ostrovul Mare(?), the refurbishing of Drobeta and the repairs within the precinct of the military part of Sucidava.
3. Constantine the Great and his followers; this is the culminating period in the fortification of the Danube's left bank and new constructions of relatively big dimensions are raised. There appear surveillance towers, too. This phase includes: Constantia-ContraMargum, Sapaja, Vrsac, Tibiscum, Moldova-Veche(?), §vinița, Dubova(?), Praetorium, Drobeta (its refurbishment), Puținei, Izvoru Frumos, Izvoarele, Desa, Bistreț, Sucidava (the exterior precinct wal), Turris, Turnu Măgurele, Dafne, Pietroasele, Piua Pietrii, Barboși, Aliobrix.
4. Valentinian I - Valens; this construction phase comprises repairs to the old fortifications. In the current research stage no new fortifications are known. Special mention should be made of the Cenad fortification's refurbishment.
5. Theodosius I; this phase is characterised mainly by the refurbishment of the fortifications destroyed or affected by the events of the year 378.
6. Arcadius - Theodosius II; it is the last phase, to be detected so far only at Sucidava. Repairs are now made throughout the limes in view of the impending invasion of the Hunes.

The End of the Fortifications
To establish the fortifications' end it is necessary to analyze the information offered by the literary sources, the stratigraphical data, the form, the size and construction elements for each and ever citadel. The geo-strategic position can provide logical arguments in this respect, and the circulation of coins can only be used very restrictively.
It is necessary to take into account first the two events that shook the whole lower Danube limes namely, the attacks of the Goths in the wake of the 378 catastrophe at Adrianopole, when Valens himself loses his life and the invasions of the Hunes in the first half of the 5th century, when the entire lower Danube limes is disaffected. Now it was that the fortifications situated beyond the Danube could not resist the Gothic shock of 378 - 379. The fortifications on the immediate banks of the Danube which were affected by this critical situation will be refurbished in part, their existence being thus pushed further in time, until the end of the 4th century or the beginning of the next one. But there are also some fortifications that ceased to exist irrespective of these chronological landmarks.
By and large, the following cessation dates can be established for the fortifications:
- Piua Pietrii, Barboși and Aliobrix cease to exist in the middle of the 4th century;
- Pojejena(?), Turnu Măgurele and Pietroasele are given up in 365;
- in 378/379 it is Cenad, Vrsac, Tibiscum, Moldova Veche, Praetorium, Puținei, Tismana-Batoți, Ostrovul Mare that are renounced;
- the end of the 4th century sees the end of Gornea, §vini?a, Dierna, Alba, Lucus, Bistre?, Dafne;
- the first half of the 5th century marks the end of Pancevo, Constantia-Contra Margum, Sapaja, Banatska-Palanka, ContraRegina, Ducepratum, Transdiana, Drobeta, Hinova, Sucidava. It appears that the destruction of these fortifications occurred in two stages: 441 and 447, when the Hunes devastate the line of the Danube up to Ratiaria at first, only to extend afterwards up to the Black Sea.
This chronogy might be modified in future, if the new research will demand it. A brief review is also provided in the paper, with rigorous pro and con arguments, of the earthworks (valla) found in the Banat and Crișana region or the northern part of Brazda lui Novac, plus the earthworks in southern Moldavia, which were erected and used in the period from Constantine the Great's reign to Valens's.
It is generally accepted that in the 4th and 5th centuries the old roads of the 2nd and 3rd centuries were used; this hypothesis is supported by the discovery of military posts in Banat and Celei. All the north-Danube roads used in the 4th and 5th centuries are ancillary ones to the strategic road of the Danube limes which traversed the southern bank of the big river.
In this period, special stress was laid on the Danube fleet which supplanted terrestrial transportats along the big river. After the lower Danube limes was made impracticable by the Hunes in the first half of the 5th century, the Empire returns to the Danube line beginning with Emperor Anastasius (in Scythia, Moesia Secunda, Dacia Ripensis) and continuing with Justinian (Moesia Prima). In what follows, the paper presents the second part of the north-Danubian fortification repertoire, which includes from the west to the east the following: Sapaja, Litterata, Recidiva, Ducepratum, Transdiana, Theodora, Ostrovul Mare, Sykibida and Dafne, although the literary sources also mention a number of others lacking in names. There are no proofs attesting that further new constructions were erected as well.
There are no fortifications in the north-Danube section of Scythia. In general, the fortifications were restored according to the older layout and dimenions. The opus mixtus construction continued to be used, but it is specified that the use of bricks predominates. The corner and median towers remain outside the precict, sometimes with modified forms. The appearance of the churches and the tombs is only documented at Sucidava.
In the current stage of research, the annexation by the Empire, in the 6th century, of a north-Danubian land strip that ran all along the big river's bank is not attested. The Roman domination was present, however, on the northern bank of the Danube, in the close vicinity of the big river. Special attention seems to have been conceded to the Banat region: of the 9 known fortifications, 6 belong to this sector. Novela XI mentions this in particular, and the general Priscus considers it to be a Roman land. The end of the fortifications should be considered to occur some time before the year 602. The fall of the Sirmium fortress under Avarre attacks seems to have represented an ill omen and, consequently, a serious threat to the entire lower Danube limes. For all the fact that the limes was disrupted in various stages, it continued in existence under the attacks of the Slavs and the Avarres, and under the circumstances of Phokas's revolt. There is no information whatsoever regarding any potential civilian settlements in the vicinity of the fortifications. If it is a fact that some older roads could continue to be used in this period, although the transport on the Danube seems more probable, the situation of the great earthworks (vallae) is quite different, as they became practically useless now, under the altered circumstances. There is no certified information either as to the construction of any bridges over the Danube.
The material presented is accompanied by two maps corresponding to the two parts of the repertoire.