Who ruled Ctesiphon?

Ctesiphon stood on the east bank of the Tigris about 35 kilometres south-east of Baghdad, in what is now Iraq. For roughly eight centuries it was a royal capital of the Iranian empires, first the Parthians and then the Sasanians, and together with Seleucia and other neighbouring towns it grew into a vast metropolis that Arabic writers called al-Mada'in, "the cities". Its one great surviving monument is the brick arch of the Taq Kasra, near the town of Salman Pak.

Ctesiphon began in the late 120s BCE as a military camp set up by the Parthian king Mithridates I across the river from Seleucia, the Greek city founded by the Seleucid Empire. The Greek geographer Strabo described it as a large village where the Parthian kings spent their winters, so as not to burden the citizens of Seleucia with their troops; in summer the court moved to Ecbatana and Hyrcania. Around 58 BCE, under Orodes II, it became the capital of the Parthian Empire, perhaps partly because the older capitals in the east were exposed to raids by steppe peoples. Over time it merged with Seleucia and nearby settlements into a single cosmopolitan city.

Its position near the western frontier made Ctesiphon a prize for Rome. The emperor Trajan captured it in 116 CE, but his successor Hadrian handed it back the following year. The Roman general Avidius Cassius took it in 164, and in 197 Septimius Severus sacked the city and sold thousands of its people into slavery.

By 226 the city belonged to the Sasanian Empire, which overthrew the Parthians and kept Ctesiphon as its capital. Under the Sasanians it grew into a great metropolis of many districts, including a royal quarter with the White Palace on the east bank and the new city of Veh-Ardashir on the west bank. Its population mixed Arameans, Persians, Greeks and Assyrians, and Zoroastrians, Jews, Christians and Manichaeans all lived there; the patriarch of the Church of the East had his seat in the city. Some accounts rank it as the largest city in the world in the late sixth and early seventh centuries.

Roman armies still came. Severus Alexander's advance in 233 ended in defeat, Carus sacked the city in 283, and in 363 the city gave its name to another battle between Roman and Persian forces. After capturing Antioch in 541, Khosrow I settled its captive inhabitants in a new town nearby, named in effect "better than Antioch". The date of the Taq Kasra, the palace's great vaulted hall, is uncertain: some historians attribute it to Shapur I in the third century, others to Khosrow I in the sixth. The Byzantine emperor Heraclius besieged the city in 627 and withdrew only when the Persians accepted his terms, and plague struck it the following year. Years of civil war between Sasanian factions followed.

After defeating the Sasanians at al-Qadisiyyah, Arab Muslim armies under Sa'd ibn Abi Waqqas occupied Ctesiphon in early 637, during the conquest of Persia by the Rashidun Caliphate. The royal family and nobles had fled, and the conquerors seized the treasury and briefly used the Taq Kasra's throne hall as a mosque. The city then declined quickly, especially after the Abbasid Caliphate founded Baghdad nearby in the 760s. The caliph al-Mansur took building material from the ruins and tried to demolish the palace for its bricks, giving up only when the task proved too large. By the end of the eighth century the city was largely deserted.

In November 1915, during the First World War, the Ottoman army defeated a British force advancing on Baghdad at Ctesiphon. German and American expeditions excavated parts of the site in 1928 to 1932, and an Italian team worked on the west bank from the late 1960s. A flood in 1888 had already brought down much of the Taq Kasra; Iraqi governments repaired it in later decades, with a restoration completed in 2017, but part of it collapsed again in March 2019. It remains one of the largest single-span brick vaults ever built.