The underground city of Ouyi (Noushabad), located 5 km north of Kashan, Isfahan province, is considered a notable piece of ancient architecture. The main reason that the underground city of Noushabad was carved stemmed from the fact that in the past, this region was insecure, suffering from raids, and by forming an underground chain of passages beneath the entire city, the inhabitants could shelter there during such attacks. Through these passages they could reach any spot in the city without being seen. The depth of this underground city varies from 4 to 18 meters. To reach the underground city there were several different openings. Some of these openings were located inside the houses of people and others were located in important gathering places, such as the main fort just outside the city. People could live in the underground passages for several days without the need of to go outside. More