The Taq Kasra is now all that remains above ground of a city that was, for seven centuries—from the 2nd century BCE to the 7th century CE—the main capital of the successor dynasties of the Persian empire: Parthians and Sassanids.

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.

circa 300-600 CE

Sasanian Era
The exact time of construction is not known with certainty. Some historians believe the founder is Shapour I who ruled Persia from 242 to 272 CE and some other believe that construction possibly began during the reign of Anushiruwan the Just (Khosrow I) after a campaign against the Byzantines in 540 CE.

Arab-Muslim Period
The structure was captured by the Arabs during the conquest of Persia in CE 637. They then used it as a mosque for a while until the area was gradually abandoned. In the early 10th century, the Abbasid caliph al-Muktafi dug up the ruins of the palace to reuse its bricks in the construction of the Taj Palace in Baghdad. The monument is also the subject of a poem by Khaqani, who visited the ruins in the 12th century.

Victorian Era
In 1851 CE French artist Eugène Flandin visited and studied the structure with Pascal Coste who remarked "the Romans had nothing similar or of the type". In 1888 CE, a serious flood demolished the greater part of the edifice. Later on the northern (right) edifice was reconstructed during the restoration program by Saddam Hussain.

Modern Era
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. From 2004 to 2008 the Iraqi government cooperated with the University of Chicago's Diyala Project to restore the site at a cost of $100,000. The Ministry of Culture also invited a Czech company, Avers, to restore the site. This restoration was completed in 2017.

circa 300-600 CE

Central Iwan
The arched iwan hall, open on the facade side, was about 37 meters high 26 meters across and 50 meters long, the largest man-made, free standing vault constructed until modern times. The arch (inspect) 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 is the largest vault ever constructed in the world. The 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.