Syria GateCircesium, known in Arabic as al-Qarqisiya, was a Roman fortress city near the junction of the Euphrates and Khabur rivers, located at the empire's eastern frontier with the Sasanian Empire. Procopius calls it the "farthest fortress" of the Romans.
History
It was later conquered by the Muslim Arabs in the 7th century and was often a point of contention between various Muslim states due to its strategic location between Syria and Iraq. The modern town of al-Busayra corresponds with the site of Circesium.