Due to the city's strategic importance and violent past the citadel of Erzurum has been rebuilt and repaired many times. However the citadel these days is little more than a shell with practically no interior buildings remaining.
A substantial fortified settlement atop a plateau above the main road from Mardin to Diyarbakir. In recent years archaeological excavation has been undertaken at the site.
The fortification of Zalabiyeh is recorded by Procopius who attributes the building of the defences to Justinian's reign. As with much of Procopius' testimony this claim must not be accepted out of hand. The remains of the defences show evidence of at least two major phases of building. The oldest phase is composed of ashlar faced walls with a rubble and concrete core, the later phase is made up of ashlars throughout. The later phase appears to have been only present in some of the towers and is certainly part of a renovation of the defences where some of the older towers needing replacing. These two different wall building techniques are mirrored across the river at the fortifications of Halabiyeh, Zalabiyeh's sister site. I have proposed that the site was not originally fortified by Justinian but was rather repaired during his reign and had older origins, potentially during the reign of Anastasius.
The impressively preserved city walls of Resafa are the subject of some debate when regards to their age and to who's reign their construction can be credited to. Scholars seem to be split as to whether they were constructed in the reigns of the Emperor Anastasius (491-518 AD) or the Emperor Justinian (527-565 AD). Procopius' attributes the first stone wall to the reign of Justinian. However this cannot be wholly accepted as fact as Procopius' accounts are occasionally deliberately misleading and sometimes wholly inaccurate. The most well preserved and impressive of the gates still extant is the Sura Gate on the north side of the city.
Regardless of which reign they were constructed in the defences do seem to be Late Antique. The walls, their covered galleries, the towers and gates were well preserved when I visited in 2010. As a result of the civil war their current condition is hard to ascertain.