Panorama view on Esfahan from the top of Marbin Fortress. 3rd largest city in Iran after Tehran and Mashhad. Esfahan has one of the largest city squares in the world, Naghsh-e Jahan Square and it is an outstanding example of Iranian and Islamic architecture. It has been designated by UNESCO as a World Heritage Site. In the 16th century Esfahan became the capitol of Persia.