Birtha (Greek: Βίρθα)[1] was an ancient fortress on the river Tigris, which was said to have been built by Alexander the Great.
It would seem, from the description of Ammianus,[1] to have resembled a modern fortification, flanked by bastions, and with its approaches defended by out-works.
From the known position of Dura, it has been inferred that the remarkable passage of the Tigris by Jovian in 363 took place near Tikrit.
This insulated cliff is separated from the town by a broad and deep ditch, which was no doubt filled by the Tigris.
At the foot of the castle is a large gate of brick-work, which is all that remains standing; but round the summit of the cliff the walls, buttresses, and bastions are quite traceable.