” … We have already indicated, in connection with the discussion of the chief figures in the pantheon, the tendency to group around the cult of the patron deity of an important centre the worship of other gods, and we have seen that this tendency goes hand in hand with the political expansion of such a centre, but that the centre is apt to retain a considerable portion at least of its religious prestige even after the political decline has set in.
The force of tradition, playing so effective a part in religion everywhere, would help to maintain rituals and practices once established, even if the conditions giving rise to such rituals and practices no longer prevailed. Confining ourselves to the larger centres and to those best known to us, like Nippur, Lagash, Uruk, Ur, Kish, Eridu, Sippar, Babylon and Borsippa in the south, and Ashur, Calah and Nineveh in the north, we note the gradual extension of the area within which the main temple stood to become a more or less extensive sacred quarter.
So in Nippur E-kur, the name of Enlil’s sanctuary, becomes such a designation to include the temples and shrines erected to the numerous deities grouped around Enlil and brought into a relationship of subserviency to their master, as his sons, daughters, servants, body-guard, ministers and officials. Similarly in Babylon, E-sagila, as the name of Marduk’s temple, grows to be a spacious quarter with numerous sanctuaries, large and small, to Nabu, Ninmakh (or Ishtar), Shamash, Ea, Nergal, Ninib to name only the most important.
The general arrangement of these temples, as we shall have occasion to see in more detail in the chapter on the architecture and art,  was in all cases the same, following an ancient prototype which provided an outer and an inner court of almost parallel dimensions, with a corridor leading from the inner court to the innermost smaller chamber, reserved for the priests and the rulers and in which, enclosed in a niche, the image of the.deity in whose honor the temple was erected stood.
Grouped around the three divisions was a series of rooms, varying in number according to the size and importance of the edifice, for the accommodation of the priests and for the administration of the temple, while in the case of the largest centres, special buildings were erected as store-houses for the temple possessions, stables for the animals, and dwellings for the numerous attendants and officials incident to the growing complications of the larger temple organizations. A feature of the main temple in every centre that was never lacking was a stage-tower, consisting of from two to seven stories, and placed either behind or at the side of the temple proper.” 
Morris Jastrow, The Civilization of Babylonia and Assyria, 1915, pp. 269-70.