Added to Unesco's World Heritage List in 1988, Sousse's 9th-century medina is an unusual and important example of Aghlabid military coastal architecture. It retains its kasbah, ramparts, Great Mosque and ribat, and still has a large residential population (35,300 at the last official census). The main pedestrian thoroughfares are Rue El Aghlaba, which runs east–west, and jam-packed Rue de France, running north–south. The most atmospheric shopping areas are Souq Er Ribba and its extension, Souq El Kayed.

The massive walls of the medina stretch 2.25km at a height of 8m and are fortified with a series of solid square turrets. They were built by the Aghlabids in AD 859 on the foundations of the city’s original Byzantine walls. Within the walls are 24 mosques (12 for men and 12 for women).

The main entrance to the medina is at the northeastern corner at Pl des Martyrs. The area was created when Allied bombs blew away this section of the wall in 1943 during WWII. Of the other gates, the most historically interesting is Bab El Finga (meaning Gate of the Blade); the French set up their guillotine just outside.