Taq Kasra

Taq Kasra, “the arch of Khosrow”, is the great vaulted hall of the Sasanian palace at Ctesiphon, on the Tigris south of modern Baghdad. Ctesiphon was the winter capital of the Parthian and Sasanian empires. The hall is traditionally attributed to Khosrow I, who reigned in the sixth century, though some scholars have argued for an earlier date.

The surviving part is a single colossal vault of fired brick, about 35 metres high and spanning some 25 metres, often described as the largest single-span brick vault of the ancient world. It opened at the front as an iwan, a hall walled on three sides and open on the fourth, where the king would have received audiences. Beside it stands one wing of a wall of blind arcades that once framed the facade.

When Arab armies took Ctesiphon in the 630s, the palace and its treasures passed into legend, and Persian and Arabic poets wrote laments at its ruins. The northern part of the facade collapsed in a flood in the nineteenth century, and the vault has suffered further damage since, prompting repeated campaigns of repair. Today the arch stands over a flat plain, a brick parabola still recognisable as the model for later iwans across Iran and beyond.