Nouakchott is not on most people's itinerary. It probably should be on more. It's a proper city on the Atlantic edge of the Sahara — not obviously pretty, not set up for tourists, genuinely itself. The market in town is worth a few hours before you head out to the beach.
Camels, horses, grilled fish, the Atlantic. I don't know how else to explain Mauritania but this is a start.