You haven't fully experienced Tunisia until you've been scrubbed down with an oven scourer by an enthusiastic elderly masseur. The oldest and most atmospheric hammams (public bathhouse) are in the medina, keeping residents steamed and cleaned. Often recognisable by their candy-striped red-and-green doorways and undecorated domes, they feel as if they haven't changed (or been cleaned) for hundreds of years. It's an amazingly exotic, sensual and relaxing experience.
You'll need a towel, and you might want a scrubbing mitt, shampoo and soap. To avoid undue attention, be aware that people don't bathe naked, but wear their underwear (men wear shorts). There are bucketloads to choose from - favourites include Zitouni. It's women-only, clean, with a good hot room; it's newer and fresher than the others.