Marrakech really touched my heart, a lot of people warned me about staying safe as i am a young blonde girl. My advice is cover up dress modestly and wear a scarf around your head if your fair and they respect that you are respecting their culture.
As for the mellah its wonderful, such vibrant colours and interesting smells and objects everywhere, my only warning would be some one will try take you everywhere and they will rip you off, find your own way. It may look like a maze but it does all join up eventually, if you are lost ask someone in a shop to get you back to the main square, they are helpful!
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.