A capital beside a river
Ctesiphon stood on the east bank of the Tigris in central Iraq, a little south-east of modern Baghdad. It is often called a Sassanian city, but it was a royal residence for the Parthian dynasty first and only later the main capital of the Sassanians, who ruled from 224 CE. Its best-known monument, the great vaulted hall called Taq Kasra, is usually linked to the Sassanian period, though who built it and when are questions without a fully settled answer.
The ruins are not a single walled city. In antiquity Ctesiphon was one of several neighbouring settlements on both banks of the river, including the older Hellenistic foundation of Seleucia. Arabic sources later called the whole cluster al-Mada’in, “the cities”.
Parthian beginnings
Seleucia on the Tigris was founded by the Seleucid dynasty around 300 BCE. When Parthian forces under Mithridates I took Mesopotamia in the 140s BCE, they chose to base their court across the river rather than inside a Greek city. Ctesiphon became a winter residence and, over time, a main seat of Parthian kings, while the royal court also travelled to other centres.
Its location mattered. The Tigris connected the region to the Persian Gulf, and overland routes led towards the Iranian plateau, Syria and, further east, the routes of the Silk Road trade routes. Caravans, soldiers and officials passed this way, and a capital here was within reach of the Roman frontier, which proved both useful and dangerous.
A target for Rome
Because Ctesiphon was close to the Roman frontier, it was repeatedly attacked. Roman armies are recorded as capturing or sacking it under Trajan in 116 CE, under Avidius Cassius around 165 CE, under Septimius Severus in 198 CE and under Carus in 283 CE. Each time the Romans withdrew and the Persian kings returned. The emperor Julian led a large army to the city’s outskirts in 363 CE but did not take it, and his campaign ended in retreat and his death. The Roman legions could win battles, but holding a distant Mesopotamian city was another matter.
These campaigns are known mostly from Roman writers, so the Parthian and Persian view is thinly recorded. That is a recurring limit on what we know about the city.
The Sassanian capital
After Ardashir I overthrew the last Parthian king and founded the Sassanian dynasty in the 220s CE, Ctesiphon became the principal capital of a state that lasted until the seventh century. The dynasty presented itself as heir to older Persian kingship and as a defender of Zoroastrianism, and its court at Ctesiphon was the centre of royal ceremony, taxation and diplomacy.
The city also took in people from elsewhere. After the Sassanian king Khosrow I captured Antioch in 540 CE, he is reported to have settled its deportees in a new town near Ctesiphon, which was modelled on the Syrian city. This kind of resettlement was one way the Sassanians gathered skills and labour to their heartland.
Taq Kasra
The surviving ruin is the front of a huge palace hall, built of baked brick. Its central feature is an open-fronted vault, or iwan, whose span is roughly 25 metres and whose height is more than 30 metres, making it one of the largest single-span brick vaults ever built. The arch rises without a supporting beam, and the builders used inclined courses of brick to build the vault, avoiding the need for heavy timber centring.
The name Taq Kasra means roughly “the arch of Khosrow”, and tradition links it to Khosrow I, who ruled in the sixth century CE. Some scholars have suggested an earlier origin, such as a palace of Shapur I in the third century. The evidence is limited, and the date remains debated. The hall was probably an audience space where the king appeared before visitors. Arabic and Persian writers praised it, and the facade originally carried tiers of blind arcades, which can be seen in old photographs and drawings.
The ruin has not stayed intact. A flood of the Tigris in the late 1880s brought down part of the facade, and the surviving section has needed conservation work since. Condition and access depend on local circumstances, so anyone planning a visit should check current information.
The Arab conquest
In the early seventh century, Sassanian Persia was exhausted. A long war with the Byzantine Empire ran from 602 to 628, and in 627 the Byzantine emperor Heraclius led a campaign into Mesopotamia that helped bring down Khosrow II. A string of short reigns followed. The young king Yazdegerd III came to the throne in 632 CE.
The Arab armies that moved into Iraq in the 630s defeated Sassanian forces at al-Qadisiyyah, with the date usually given as around 636 CE, though sources vary. The Arab commander Sa’d ibn Abi Waqqas then crossed the Tigris and took Ctesiphon around 637 CE. Yazdegerd III had already left, and he fled east, where he was killed in 651 CE. The fall of Ctesiphon is a key step in the story of the first Islamic empire.
Later tradition says that the Arab troops prayed in the Sassanian hall, and that the palace treasures were taken as spoils. Accounts of such details were written down generations later and may have been shaped by legend.
Decline of the city
Ctesiphon was not destroyed overnight. Its role passed to new centres, notably Kufa and Basra, and then to Abbasid Baghdad, founded in 762 CE a short distance upriver. Accounts say brick and building material from the old cities was reused in the new capital, and a story is told that the caliph al-Mansur considered demolishing Taq Kasra but found the task too costly. Whatever the truth, the site was gradually abandoned, and the arch outlasted the city around it.