Upi or Opis, on the Tigris, still farther to the north, lay outside the boundaries of primaeval Chaldaea.
East of Babylonia were the mountains of Elam, inhabited by non-Semitic tribes.

Among them were the Kassi or Kossaeeans, who maintained a rude independence in their mountain fastnesses, and who, at one time, overran Babylonia and founded a dynasty there which lasted for several centuries.

The capital of Elam was Susa or Shushan, the seat of an early monarchy, whose civilisation was derived from the Babylonians.
In the south the Tigris and Euphrates made their way to the region of salt-marshes, called Marratu in the inscriptions, Merathaim by the prophet Jeremiah.

They were inhabited by the Semitic tribe of the Kalda, whose princes owned an unwilling obedience to the Babylonian kings.

One of them, Merodach-baladan, succeeded in making himself master of Babylonia, and from that time forward the Kalda became so integral a part of the population as eventually to give their name to the whole of it.