Ctesiphon

Ctesiphon (TESS-if-on, Middle 𐭲𐭩𐭮𐭯𐭥𐭭, Tyspwn or Tysfwn, ῶ, Attic [ktɛːsipʰɔ̂ːn], Syriac) was an ancient city in modern Iraq, on the eastern bank of the Tigris, about 35 kilometres (22 mi) (22 mi) southeast of Baghdad. Ctesiphon served as a royal capital of the Iranian empires for over eight hundred years, in the Parthian and Sasanian periods. It fell in 637, during the Muslim conquest of Persia. Ctesiphon developed into a rich commercial metropolis, merging with the surrounding cities along both shores of the river, including the Hellenistic city of Seleucia. Ctesiphon and its environs were therefore sometimes referred to as "The Cities" (Mahuza, al-Mada'in). In the late 6th and early 7th century, it was listed as the largest city in the world by some accounts. During the Roman–Parthian Wars, Ctesiphon fell three times to the Romans, and later fell once during Sasanian rule. It was also the site of the Battle of Ctesiphon in 363 AD. After the Muslim invasion and conquest, the city fell into decline and was depopulated by the end of the 8th century, its place as a political and economic center being taken by Baghdad, the Abbasid capital. The most conspicuous structure remaining today is the Taq Kasra, sometimes called the Arch of Ctesiphon.

Archaeological site data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).