Coordinates: 33°5′37.4″N 44°34′50.6″E / 33.093722°N 44.580722°E / 33.093722; 44.580722
The Tāq-e Kisrā (Persian: طاق كسرى), also called Iwān-e Kisrā (Persian: إيوان كسرى meaning Iwan of Khosrau), is a Sassanid-era Persian monument in Al-Mada'in which is the only visible remaining structure of the ancient city of Ctesiphon. It is near the modern town of Salman Pak, Iraq.History
Construction began during the reign of Khosrau I after a campaign against the Byzantines in 540 AD. The arched iwan hall, open on the facade side, was about 37 meters high 26 meters across and 50 meters long, the largest vault ever constructed at the time.
The arch was part of the imperial palace complex. The Throne room—presumably under or behind the arch—was more than 30 m (110 ft) high and covered an area 24 m (80 ft) wide by 48 m (160 ft) long. The top of the arch is about 1 meter thick while the walls at the base are up to 7 meters thick. It was the largest vault ever constructed in Persia. The inverse catenary arch was built without centring. In order to make this possible a number of techniques were used. The bricks were laid about 18 degrees from the vertical which allowed them to be partially supported by the rear wall during construction. The quick drying cement used as mortar allowed the fresh bricks to be quickly supported by those that were previously laid.
The Taq-i Kisra is now all that remains above ground of a city that was, for seven centuries, the main capital of the successor dynasties of the Seleucids, Parthians and Sassanids of Persia. The structure left today was the main portico of the audience hall of the Sassanids who maintained the same site chosen by the Parthians and for the same reason, namely proximity to the Roman Empire whose expansionist aims could be better contained at the point of contact.
The structure was captured and looted by Arabs in AD 637. They then used it as a mosque for a while until the area was gradually abandoned.
In 1888 floods destroyed a third of the ruins.
The monument was in the process of being rebuilt by Saddam Hussein's government in the course of the 1980s, when the fallen northern wing was partially rebuilt. All works, however, stopped after the 1991 Persian Gulf War. The Iraqi government is cooperating with the University of Chicago's "Diyala Project" to restore the site.
Alternative names and spellings include: Tâgh-i Kasrâ, Ayvan-e Khosrow, Ayvan-a Kesra, Ayvān-a Kesrā, Ayvān-e Madā'en, Taq-i Khusrau, Taq i Kisra, Iwan-i Kisra, Taq-e Kisra, Tagh-i Kasra, Great arch of Ctesiphon.