I went on a family vacation to Marrakech in 2008 (both my brother and I were in our twenties) and we had a blast. Located in northwest Africa, it doesn't feel like what I normally associate with "Africa," but rather more Middle Eastern. It is so unlike any place I've ever been to.
We stayed at a traditional riad (similar to an inn, with an open courtyard in the center of the building/house) in the old town to get the authentic experience. Walking around the old town, and especially the Medina (huge market in the center of old town) was a feast for the senses. The night market was a throb of people where you could expect to see everything from food carts selling made-to-order food and drink (not alcoholic of course!) to snake charmers and men doing other tricks. Definitely a must-do experience if ever in Morocco.
One thing to note is to bring the number of your hotel/guide with you! It is incredibly easy to get lost in the old town with its windy paths and "streets" with no street signs that we saw. We learned our lesson after the first night and began keeping track of landmarks to find our way home after dark.