We revisited the Via Domitia. There’s a later mill immediately upstream from the remains of this structure. We saw pretty small fishies in the water, and slightly larger fishies keeping them company. Seems like there should have been even larger ones, but we didn’t see them.
This is the strangest anti-irrigation engineering feat I can remember encountering anywhere. These radiating (actually pointing inward) canals brought water to the center of this circular area, sending the flow out through a drain, making a large marshy area useful for agriculture. This was done in the…13th C. I can’t tell who masterminded this project, or who funded it.