Since antiquity the two mighty rivers of the Mesopotamian valley have given, and they have taken away. One year's flood deposited precious topsoil; the second swept it away. Kings built great towers and cities of baked bricks; time, conquerors and the Tigris and Euphrates littered the plains with their sun-bleached ruins.
One such city was Ctesiphon: once a sumptuous capital near the shifting banks of the meandering Tigris River about 20 miles south of modern Baghdad, now no more than the dusty shell of a palace with, miraculously, one great vault still arching across the dull monotony of the arid plain.
In 144 B.C., as part of an Asiatic reaction against Hellenism, a race of people called the Parthians swept out of the region east of the Caspian, invaded Babylonia and established a camp on the east bank of the Tigris opposite the Greek city of Seleucia. The camp was called Ctesiphon and grew to be, first, the winter residence of the Part'hian kings, a "royal suburb," and then a great city in itself—a city that, according to one historian, "first rivalled and then eclipsed" Seleucia as the capital of the Empire. An interesting difference in the cities is that Ctesiphon's plan—typically Parthian—was circular, in contrast to the rectangular Greek layout of its sister across the river. Some coins of fhe first century show the goddesses of the twin cities joining hands across an altar.
But during the next few centuries the cities were often a battle ground as Roman legions under Trajan, Avidius Cassius and Septimius Severus in turn, struggled to capture and hold them.
Finally, about A.D. 224, the Sassanians, rebuilding the Persian Empire after five centuries of subjugation—first to Alexander and the Seleucids, then to the Parthians—made Ctesiphon their capital, it flourished from the wealth flowing in from a lucrative silk trade with China and became a center of Nestorian Christianity and learning.
It was during the rule of the Sassanians that the great palace called by the Arabs Taq-e Kisra was built at Ctesiphon. Some archeologists believe it dates back as early as the fourth century but local Arab tradition holds that it was constructed during the time of King Khusrau I who reigned from 590 until 628 when the city was devastated by the Byzantine emperor Heraclius. Tradition also says that the facade of the mud palace was covered with gold and silver and that beneath the great vault lay a vast carpet woven to resemble a garden, with silver paths, streams of pearls, and flowers of emeralds. Some splendid murals, at least, are known to have remained intact as late as the 9th century.
The empty vault of mud brick that stands today is a far cry from the splendor envisioned in the legends but what remains of Ctesiphon is enough to stir the imagination still. One eminent world traveler and writer has called it "... one of the most impressive architectural constructions that I know." Of the great elliptical barrel vault he adds, "... its curve hangs over empty nothingness in an uncanny way."
The arches of the vault were constructed, in fact, over empty space without the use of temporary wooden centering—a technique not uncommon in Mesopotamia, but amazing on such a scale. The lower portion of the vault was built according to the corbel principle. Thin mud bricks were stepped inward in successive horizontal courses, each projecting a bit further over the hall. in Khusrau's palace the bricks had a slight backward slant against the end walls, although the corbel arch, unlike the true arch, exerts no outward thrust but is held up by the sheer weight of these massive walls on each side. At approximately half height the construction changed to the normal arch principle. The successive brick arches which form the vault had staggered joints to provide sufficient bond which, together with the steep parabolic shape of the arch, allowed its construction without complete centering from the ground. The Sassanians were masters of the art and constructed other huge vaults such as the one—now collapsed—at Firuzabad in Iran. The span of the vault at Ctesiphon is 82 feet and at the crown it is 120 feet above the ground.
The vault is open to the east, to make a kind of open porch or iwan common in later Muslim architecture, and the Sassanid builders may have inspired the vaulted entrances of later Persian mosques.
Attached to the vault at Ctesiphon, one wall of the south wing of the palace also remains. On the interior side of this wall can be seen the toothings of smaller vaults for the original two upper floors which have collapsed.
The neo-Persian Empire ended with the fall of the Sassanid dynasty in the 7th century. One of the final blows came in 637 A.D. when Arabs occupied Ctesiphon and Seleucia which they called al-Madam, the "capitals". They used the decaying buildings as quarries for building materials but the great palace still stood and was used for a while as an improvised mosque.
When the Abbasids decided in the 8th century to build their capital at Madinet as-Salam, "the city of peace" (present-day Baghdad), they abandoned what was left of the two cities. Caliph al-Mansur even wanted to destroy the palace of Khusrau but happily, his Persian adviser was able to dissuade him by arguing that demolition costs would be too high.
The river was not subject to such reason, however, and over the centuries it continued to lick at the mud bricks of the palace and add their silt to its delta.
An aerial survey has shown, in fact, that the course of the Tigris has shifted markedly in modem times, no longer flowing between the ancient twin cities but now cutting through the site of Sassanid Ctesiphon. As recently as 1909 a flood swept away the north wing of the palace.
Today, as Iraq strives to protect this relic of the past, great flocks of wintering storks nest safely out of reach on the thin egg-shell vault high above the heads of village children playing in the shade of the cavernous interior, and camera-laden tourists drive out from Baghdad before breakfast to catch the morning sun on the eastern facade. But the Tigris, like a great full-bellied cat, flows on nearby—waiting.
William Tracy is Assistant Editor of Aramco World Magazine.