Protection against River Arno floods.

Pisa and Florence (and other lesser known towns in between) live with the constant threat of floods from the Arno. Over the years some interventions along the course of the river have improved their management (mostly in strengthening embankments and establishing "overflow" areas where flood waters can be directed to lessen the pressure), but at times these last ditch defences might still have to be resorted to, especially in the two cities where changes to the river course or embankments are of course harder to effect. This is a great illustration of that constant threat, Dimas. Anyone who knows Pisa would recognize this and know what it means.

A very belated HFF!