Birtha (Mesopotamia) bastions are quite traceable. There are the ruins of a vaulted secret staircase, leading down from the heart of the citadel to the water's edge. Birtha (Mesopotamia) Birtha () 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, to have resembled a modern fortification, flanked by bastions, and with its approaches defended by out-works. Shapur II here closed his campaign in 360, and was compelled to retire with considerable loss. D'Anville and Edward Gibbon both identify Birtha as modern-day Tikrit, Iraq. The
Agriculture in ancient Mesopotamia is very arid and has poor soil quality. But the man-made infrastructure took advantage of some of the potential of this space (large rivers and broad, flat plains) to counter these issues and make lower Mesopotamia one of the most productive agricultural areas in the ancient world. In the north, the uncertainties of production were greater, as a result of the fluctuation of the climate year by year. There were, as a result, many systems of agricultural land, reflecting the diversity of ancient Mesopotamian agriculture. The natural context of ancient Mesopotamia was little different from modern conditions in this region,