50 BCE) in the Bibliotheca Historica:[3] "After all these in a low ground in Babylon, she sunk a place for a pond, four-square, every square being three hundred furlongs in length, lined with brick, and cemented with brimstone, and the whole five-and-thirty feet in depth: into this having first turned the river, she then made a passage in form of a vault, from one palace to another, whose arches were built of firm and strong brick, and plaistered all over on both sides with bitumen, four cubits thick.

She made likewise two brazen gates at either end of the vault, which continued to the time of the Persian empire.

"Philostratus (d. 250 CE) also describes the tunnel's construction in the Life of Apollonius of Tyana:[5][6] "And [Babylon] it is cut asunder by the river Euphrates, into halves of similar shape; and there passes underneath the river an extraordinary bridge which joins together by an unseen passage the palaces on either bank.

The foundations were thus made stable, and also the walls of the tunnel; but as the pitch required water in order to set as hard as stone, the Euphrates was let in again on the roof while still soft, and so the junction stood solid".Construction allegedly began with a temporary dam across the Euphrates, and proceeded using a "cut and cover" technique.

[2] It is presumed that it was used by pedestrians and horse driven chariots and connected a major temple with the royal palace on the other shore of the river.