An iwan (eyvān)'s defined as a vaulted hall or space, walled on three sides, with one end entirely open. Iwans were a trademark of the Sassanid architecture of Persia, later finding their way into Islamic architecture. This transition reached its peak during the Seljuki era, when iwans became established as a fundamental design unit in Islamic architecture. Typically, iwans open on to a central courtyard, and have been used in both public and residential architecture. The Great Iwan of Cai… (More on Iwan)