The Babylonians, in coalition with the Medes and Scythians, defeated the Assyrians in 612 BC and sacked Nimrud and Nineveh, starting the so-called 'Neo-Babylonian' age, manifested architecturally at Babylon, the capital. This huge city, which had been destroyed in 689 BC by the Assyrian Sennacherib, was restored by Nabopolassar and his son Nebuchadnezzar II. Divided by the Euphrates, it took 88 years to build and was surrounded by outer and inner walls. Its central feature was Esagila, the temple of Marduk, with its associated seven-story ziggurat Etemenanki, popularly known later as the Tower of Babel. The ziggurat reached 91m in height and had at the uppermost stage a temple (a shrine) built of sun-dried bricks and faced with baked bricks.

From the temple of Marduk northward passed the processional way, its wall decorated with enamelled lions. Passing through the Ishtar Gate, it led to a small temple outside the city, where ceremonies for the New Year Festival were held. West of the Ishtar Gate were two palace complexes; east of the processional way lay, since the times of Hammurabi, a residential area. Like Babylon's famous Hanging Gardens, one of the Seven Wonders of the World, little of the city remains.

Archaeologists discovered a core consisting of the ruins of previous ziggurats which had been levelled and enlarged serval times, before Nebuchadnezzar added a casing of burnt brick 15m thick. Of this structure only the ground plan and traces of the three stairs leading up to it have been preserved.

The Ishtar Gate is one of the few surviving structures. The glazed-brick facade of the gate and the processional way that led up to it were excavated by German archaeologists and taken to Berlin, where the monument was reconstructed. The large complex, some 30m long, is on display in the city's Vorderasiatische Museum. On the site of ancient Babylon, restoration of an earlier version of the Ishtar Gate, the processional way, and the palace complex, all constructed of unglazed brick, has been undertaken by the Iraq Department of Antiquities.

In 539 BC the Neo-Babylonian kingdom fell to the Persian Achaemenid king Cyrus the Great. Mesopotamia beame part of the Persian Empire, and a royal palace was built at Babylon, which was made one of the empire's administrative capitals. In approximately 478 BC, Babylon had been taken over by the Persian King Xerxes who crushed a rebellion there that year. The tower was neglected and crumbled.

In 440 BC Herodotus wrote that the ancient city of Babylon, "In addition to its size... surpasses in splendor any city in the known world." He claimed that the outer walls were 56 miles in length, 80 feet thick and 320 feet high. Wide enough, he said, to allow a four-horse chariot to turn.Inside the walls were fortresses and temples containing immense statues of solid gold.

After Alexander the Great conquered the Persians, he also planned to rebuild the tower, and most of the debris had been removed in preparation for its reconstruction when he died.

While archaeological examination has disputed some of Herodotus's claims (the outer walls seem to be only 10 miles long and not nearly as high), his narrative does give us a sense of how awesome the features of the city appeared to those that visited it.