While roaming around the old Medina of Tunis, you may look around and above you to admire the medieval islamic architecture but you rarely think of looking down, to your ankle level.
All around the medina’s streets there is some hidden metal round markers, indicating the level of elevation compared to sea level.
and yes Tunis is not a very elevated place, the Mean sea level is as you can see between 7 to 23 meters.
Those are the markers that i personally sniffed out, it seems that there were more all around but many of them were destroyed, removed or built upon them.