You really can't miss Koutoubia Mosque; it's visible from all over Marrakech and kind of becomes your landmark when you're trying not to get lost. Even though non-Muslims can't go inside, it's still worth walking by to admire the architecture and the gardens surrounding it. We found ourselves passing it multiple times throughout our stay, and it was a nice break from the chaos of the medina. If you're exploring Marrakech on foot, chances are you'll end up here at least once.