bridges

   Not many large-scale, permanent bridges were built in ancient Mesopotamia, partly because supplies of stone and timber were fairly scarce on the Mesopotamian plains. Also, the Tigris and Euphrates rivers tended to shift their courses from time to time, rendering permanent bridges obsolete. As a rule, people forded rivers by using rafts and small boats as ferries. or sometimes pontoon bridges, temporary structures made by laying boards across rows of boats, were constructed. These were especially useful for moving armies across waterways, as in the case of the bridge of boats erected by Persia's King Xerxes I to get his men across the Hellespont on the way to invade Greece in 480 b.c.

   Nevertheless, a few major, permanent bridges were built in ancient Mesopotamia. One, erected by King Nabopolassar circa 600 b.c. across the Euphrates in Babylon, is the oldest-known large-scale, permanent bridge in the world. The Greek historian Herodotus, who saw this bridge when he visited Babylon in the fifth century b.c., describes its construction:

   [The builder] ordered long stone blocks to be cut, and when they were ready . . . diverted the river into [a pre-dug] basin. And while the . . . original bed of the stream was drying up, [the builder erected] an emban kment on each side of the water's edge ...thenbuiltabridgeovertheriver with the blocks of stone which had been prepared, using iron and lead [clamps] to bind the blocks together. Between the piers [vertical supports] of the bridge, squared lengths of timber [were] laid down for the inhabitants to cross by. ... Finally, when the ... bridge [was] finished, the river was brought back into its original bed. (Histories 1.186)

   The remains of this impressive structure have been excavated and reveal that it was 380 feet (115m) long and rested on seven massive stone piers. The engineering was sound enough that the bridge was still in use at least six hundred years later, when another Greek historian, Diodorus Siculus, saw it.

   Another noteworthy Mesopotamian bridge was one built by the Assyrian king Sennacherib to carry the water channel of an aqueduct across a stream. Located at Jerwan, north of Nineveh, the bridge was some 90 feet (27m) long and 30 feet (9m) high and rested on five stone arches made of stone blocks measuring 20 inches (51cm) on a side. The king's inaugural inscription can still be read, proclaiming, in part, "I caused a canal to be dug to the meadows of Nineveh. I spanned a bridge of white stone blocks. These waters I caused to pass over it."

   See also: building materials and methods; water supplies