I would say, the people in the first place. You will find joyful people everywhere, happy and ready to make your day by a beautiful smile, good music “Dakka Marakchia” a well-known musical form.
Yes, the people are great, but what makes Marrakech the most desired city by tourists is Food. Marrakech is the best location to find some great eating options. There are many French style cafés, bistros, and restaurants. The food stalls at the Djemaa el Fna are a must try that offer many inexpensive Moroccan style traditional cuisines.
Last but not least, the secrets (the unique places, art..) that this city keeps under wraps.