Taq Kasra "Ctesiphon" are the remains of a Sasanian-era Persian monument, dated to c. the 3rd to 6th-century, which is sometimes called the Arch of Ctesiphon. It is located near the modern town of Salman Pak, Iraq. It was the facade of the main palace in Ctesiphon, and is the only visible remaining structure of the ancient capital city. The archway is considered a landmark in the history of architecture, and is the second largest single-span vault of unreinforced brickwork in the world after Gav