SHUSHTAR

town, southwestern Iran. It is situated on a small plateau below the confluence of the Karun River with one of its minor tributaries. Many of the town's stately houses of stone and brick have cellars, called zir zamin, to provide a cool shelter from the terrible summer heat, which may reach 128 F (53 C). The town was once a major trade centre and dominated an extensive area of irrigated agriculture, but it is now declining. Shushtar is famous for its great engineering works constructed in ancient times for the disposal and use of the waters of the Karun River. Shushtar's little plateau sits between the main arm of the Karun and an artificial channel more than 100 feet (30 m) deep, and the city itself is crossed by small canals that use the Karun's water. But the most impressive works are three large dams built in Sasanian times (AD 224651) to regulate the river and the artificial channel's flow and maintain water levels for irrigation. The greatest of these dams, the Band-e Qeysar, was originally 1,800 feet (550 m) long and supported on its numerous arches Valerian's Bridge, so called because it was constructed under the Sasanian king Shapur I (d. AD 272) using Roman engineers and other prisoners-of-war captured along with the emperor Valerian in 260. To prevent erosion of the riverbed above the dam, the bed was paved with huge stone slabs bound together with iron. The monumental dam was regarded by later Arab conquerors as one of the wonders of the world. But only about 35 of its arches remain, and it is now in ruins. The final decay of the dam system in the 19th century spelled the collapse of both Shushtar's irrigation network and its prosperity, although several waterwheels on the canals are still used to drive numerous small flour mills and to generate electricity. Pop. (1986) 65,840.