Lately, pictures of the Shushtar
waterworks in

Localizing Shushtar on a map is one thing but linking it to a known city or river is another matter. Then I read that the water was diverted from the Karun River using manmade canals dug through the natural rock.
The above makes me believe that Alexander must have seen this intricate water complex. Thanks to a systems of qanats (see: The qanats, one of the greatest inventions of mankind), the river provided water for domestic use and irrigation of the surrounding agricultural fields. Surprisingly, the main crop was sugar cane.
Over the centuries, the infrastructure was improved with more canals, tunnels, dams, and watermills. In the early years of the Sassanid Empire, starting in 224 AD, Shushtar occupied an island in the middle of the Karun River and became the summer capital of the kings. The city was reachable from the east, west, and south through entrance gates and bridge crossings.
Three large dams were built by the Sassanids between 224 and 651 AD. They regulated the river and the manmade channel’s flow to supply water to the city and cultural land around it.
To prevent erosion, the riverbed above the dam was paved with large slabs tied together with iron clamps.
The pictures of Shushtar reveal how impressive these waterworks were. Later Arab conquerors defined Shushtar as one of the wonders of the world.