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
Mesopotamia land, declining over time as royal and other private holdings increased in frequency. The word Ensi was used to describe the official who organized the work of all facets of temple agriculture. Villeins are known to have worked most frequently within agriculture, especially in the grounds of temples or palaces. The geography of southern Mesopotamia is such that agriculture is possible only with irrigation and good drainage, a fact which has had a profound effect on the evolution of early Mesopotamian civilization. The need for irrigation led the Sumerians, and later the Akkadians, to build their cities along the Tigris