Lower Mesopotamia
In contrast with the arid plateau of Mesopotamia stretched the rich alluvial plain of Chaldea, formed by the deposits of the two great rivers that encircled it. The soil was extremely fertile, and teemed with an industrious population. Eastward rose the mountains of Elam, southward were the sea-marshes and the Kaldy or Chaldeans and other Aramaic tribes, while on the west the civilization of Babylonia encroached beyond the banks of the Euphrates, upon the territory of the Semitic nomads (or Suti). Here stood Ur (Mugheir, more correctly Muqayyar) the earliest capital of the country; and Babylon, with its suburb, Borsippa (Birs Nimrud), as well as the two Sippars (the Sepharvaim of Scripture, now Abu Habba), occupied both the Arabian and Chaldaean sides of the river. The Arakhtu, or "river of Babylon," flowed past the southern side of the city, and to the southwest of it on the Arabian bank lay the great inland freshwater sea of Najaf, surrounded by red sandstone cliffs of considerable height, 40 miles (64 km) in length and 35 in breadth in the widest part. Above and below this sea, from Borsippa to Kufa, extend the famous Chaldaean marshes, where Alexander the Great was nearly lost (Arrian, Eup. Al. vii. 22; Strabo xvi. I, § 12); but these depend upon the state of the Hindiya canal, disappearing altogether when it is closed.
Eastward of the Euphrates and southward of Sippara, Kutha and Babylon were Kish (Ultaimir, 9 miles (14 km) E. of Hillah), Nippur (Niffer)-where stood the great sanctuary of El-lu, the older Bel-Uruk or Erech (Warka) and Larsa (Senkera) with its temple of the sun-god, while eastward of the Shatt el-Hai, probably the ancient channel of the Tigris, was Lagash (Tello), which played an important part in early Babylonian history.
The primitive seaport of the country, Eridu, the seat of the worship of Ea the culture-god, was a little south of Ur (at Abu Shahrain or Nowäwis on the west side of the Euphrates). It is now about 130 miles (210 km) from the sea; as about 46 inches of land have been formed by the silting up of the shore since the foundation of Spasinus Charax (Mu/-zamrah) in the time of Alexander the Great, or some 115 feet (35 m) a year, the city would have existed perhaps 6000 years ago. The marshes in the south, like the adjoining desert, were frequented by Aramaic tribes; of these, the most famous were the Kaldä or Chaldaeans who under Merodach-baladan made themselves masters of Babylon and gave their name in later days to the whole population of the country. The combined stream of the Euphrates and Tigris as it flowed through the marshes was known to the Babylonians as the ndr marrati, "the salt river" (cp. Jeremiah 1:21), a name originally applied to the Persian Gulf.
The alluvial plain of Babylonia was called Edin, though the name was properly restricted to "the plain" on the western bank of the river where the Bedouins pastured the flocks of their Babylonian masters. This "bank" or kisad, together with the corresponding western bank of the Tigris (according to Fritz Hommel the modern Shatt el-Uai), gave its name to the land of Chesed, whence the Kasdim/Kasdin of the Old Testament. In the early inscriptions of Lagash, the whole district is known as Gu-Edinna, the Sumerian equivalent of the Semitic Kisad Edini. The coastland was similarly known as Gu-gbba (Semitic Kisad tamtim), the "bank of the sea."
A more comprehensive name of southern Mesopotamia was Kengi, "the land," or Kengi Sumer, "the land of Sumer". Sumer has been supposed to be the original of the Biblical Shinar and the Sankhar of the Amarna letters. Opposed to Kengi and Sumer were Urra (Un) and Akkad or northern Babylonia. The original meaning of Urra was perhaps "clayey soil," but it came to signify "the upper country" or "highlands," kengi being "the lowlands." In Semitic times, Urra was pronounced Un and confounded with uru, "city" as a geographical term, however, it was replaced by Akkadu (Akkad), the Semitic form of Agade - written Akkattim in the Elamite inscriptions - the name of the elder Sargon's capital. The rise of Sargon's empire was the probable cause of this extension of the name of Akkad; henceforward in the imperial title, "Sumer and Akkad" denoted the whole of Babylonia. After the Kassite conquest of the country, northern Babylonia came to be known as Kar-Duniyash, "the wall of the god Duniyask," from a line of forts similar to that built by Nebuchadrezzar between Sippara and Opis, to defend his kingdom from attacks from the north. As this last was "the Wall of Semiramis" mentioned by Strabo (xi. 14. 8), Kar-Duniyash may have represented the Median Wall of Xenophon (Anab. ii. 4. 12), traces of which were found by F.R. Chesney extending from Fallujah to Jibbar.
Read more about this topic: Geography Of Mesopotamia