Taq Kasra

Tāq Kasrā (also known as Taq-i Kisra or Arch of Ctesiphon) is the ruins of a Sasanian-era Persian monument dating to c. the 3rd to 6th centuries AD[1]. Located near modern Salman Pak, Iraq, it formed the grand facade of the main palace in the ancient capital of Ctesiphon[2]. The structure is the only visible remainder of the once-magnificent city and represents a landmark in architectural history[3]. Its enormous brick archway features the world's second-largest single-span unreinforced vault, surpassed only by Iran's Gavmishan Bridge[1].