Rising from the desert seemingly in the middle of nowhere, this fortified settlement was built in Byzantine times as a defense against the Sassanian Persian threat.  The site itself has even earlier roots, and is even mentioned in the Old Testament.  It gained importance with the rise of the cult of St. Sergius, a Roman soldier who was martyred in 305 after refusing to sacrifice to the Roman God Jupiter.

The Byzantine emperor Anastasius renamed the city Sergiopolis in the saint’s honor, and added a number of the structures which may still be seen today: an enormous basilica, built to accommodate large numbers of pilgrims, frieze-adorned ramparts, and cathedral-like underground cisterns that produce a haunting echo.