Taq Kasra or Ctesiphon

A historic landmark Called Taq Kasra or Ctesiphon
was an ancient city, located on the eastern bank of the Tigris, and about 35 kilometres (22 mi) southeast of present-day Baghdad. Ctesiphon served as a royal capital of the Persian Empire in the Parthian and Sasanian eras for over eight hundred years.[2] Ctesiphon remained the capital of the Sasanian Empire until the Muslim conquest of Persia in 651 AD

It is located near the modern town of Salman Pak, Iraq. It is the only visible remaining structure of the ancient city of Ctesiphon. The archway is considered a landmark in the history of architecture,and is the largest single-span vault of unreinforced brickwork in the world
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