In the Library of the Institute of Archaeology, London, there is a collection of aerial photographs of Iraq taken by the R.A.F. during the 1930s. One of a pair, taken near Zairwan (36° 26′ N; 41° 59′ E) demands publication for the information it gives on the extent and structure of the Roman limes (Plate XX).

The photograph shows a stretch of wall with faces of large orthostats and filled with material whose nature cannot be determined from the picture. The wall runs along a low ridge. There are remnants of other structures against the wall and others, less well preserved, spreading down the slope of the ridge. These structures seem to be of poor masonry and almost certainly post-date the wall itself. There is no reason to suggest that they have any rôle in connection with the functioning of the wall. On the other side of the ridge are clear traces of what is probably a road with small mounds running along either side of it.

Zairwan is north of Jebel Sinjar and to the north-east of the important town of Singara. It stands at the foot of the mountains and gives its name to a pass of no great quality running through them.