Proximity to Ctesiphon
Baghdad was close to the Sasanian ruins of Ctesiphon, and ‘Abbasid authors questioned whether or not to remove remnants of the pre-Islamic past.
Taq-e Kisra, or the Iwan of Khosrow
This is one of the remnants of “the cities” of Ctesiphon, built sometime between the 3rd and 6th centuries.

A 9th-century Description
This passage is from Ya’qubi, a Persian bureaucrat who lived in the 9th century.
Al-Mada’in [“the cities”] was the seat of Persia’s kings and was founded by Anushirvan. It consists of several cities on the banks of the Tigris. On the eastern bank is the city that was called ‘the ancient’ [city], in which there is the old White Palace, whose builder is not known, and the congregational mosque, which was built by the Muslims at the conquest. Also on the eastern bank is the city named Asbanbar, in which is the great Iwan of Kisra, of which the Persians have nothing similar, its roof rising to 80 cubits. Between the two cities there is a distance of a mile. In this city [of Asbanbar], Salman al-Farisi and Hudhayfa b. al-Yaman [early Muslims involved in the conquest of Iran] settled, and their graves are in it. Adjacent to these cities is a city called Rumiyya, built, it is said, by the Romans when they conquered the kingdom of Persia. It was there that the amir al-mu’minin al-Mansur was when he killed Abu Muslim.
Source, pp. 172-3.
An 11th-century Description
This passage comes from an 11th-century text by al-Khatib al-Baghdadi. He writes that a Persian secretary convinced the ‘Abbasid caliph Mansur to leave the ruins.

Source, pp. 177.
Circular City
A Modern Interpretation of Baghdad

Aerial Images of Other Ancient Iranian Cities
Darabgird

Firuzabad [Ardeshir-Xwarrah]
