It consists chiefly of a series of rich and productive plains, lying along the courses of the various tributaries which flow from Mount Zagros into the Tigris, and often of a semi-alluvial character.

These plains are not, however, continuous.
Detached ranges of hills, with a general direction parallel to the Zagros chain, intersect the flat rich country, separating the plains from one another, and supplying small streams and brooks in addition to the various rivers, which, rising within or beyond the great mountain barriers, traverse the plains on their way to the Tigris.

The hills themselves--known now as the Jebel Maklub, the Ain-es-sufra, the Karachok, etc .-- are for the most part bare and sterile.

In form they are hogbacked, and viewed from a distance have a smooth and even outline but on a nearer approach they are found to be rocky and rugged.

Their limestone sides are furrowed by innumerable ravines, and have a dry and parched appearance, being even in spring generally naked and without vegetation.