Shushtar is a city built on water. On the Karun river in the south-west of Iran, in the province of Khuzestan, it grew up around an ancient system of dams, canals and mills that is now a UNESCO World Heritage site. The engineers of the Sasanian period diverted the river into a long canal, the Gargar, that runs through the city and drives a series of watermills, and then it falls in waterfalls into a lower channel. A great weir, the Band-e Kaisar, was built, according to tradition, by Roman prisoners captured when the Persian king Shapur I defeated the emperor Valerian in the third century.
The town has about 77,000 people, so fuel and food are easy. The old quarter, with its narrow lanes, has houses with cool cellars called sardab, where families once took refuge from the heat. The ruins of the Salasel Castle, a fortress on an island in the river, rise over the old canal, and the mill complex is a maze of tunnels, chambers and stone wheels that you can walk through.
The heat is the main thing to know. In summer, temperatures regularly pass forty-five degrees, and the air is heavy and still, so the best time to ride in Khuzestan is from November to March, when the days are warm and the nights cool. The roads across the plain are flat, straight and fast, with oil pipelines and date palms along the way, and wind-blown dust can reduce visibility. Dezful, a neighbouring city, has its own old bridge and quiet streets.
Further south, the marshes of southern Iraq, home of the Marsh Arabs, form a similar water landscape across the border, and the two regions share a long history. Stay out of the midday sun, drink plenty of water, and let the evening bring you out into the old streets, where the sound of water echoes from the walls.