Although I had heard about this term before, visiting these medina's offered a real experience . A Mednia, essentially a small city, with narrow lanes, densely populated and protected by fort like walls, offer a rustic experience. The small walled cities were designed to protect the residents against attacks and pirates.
The medina in Tunis is full of small time shop keepers, and medina of Hammamet is specially made for 'Tourists', it doesn't have 'authenticity'. Nonetheless, you have to be in Soussse's Medina to have a close look in to the life in Medinas. The Medina in sousse is one of the most authentic medina I saw in Tunisia.
The medina of Sousse is a fomouse one and the visit is not complete without the medina.
Find out more about Medinas on Wikipedia
Check the links for places with in Sousse
A view of horizon from Port El Kantaoui