When I went to Marrakech with my mum before Christmas, we did a day trip to the Atlas Mountains (in addition to a day trip to Essaouira, which you can read about here). The Atlas Mountains is the longest mountain range in Africa, stretching through Morocco, Algeria and Tunisia. Because we only went for a day, we did not get to see much; we only saw Ourika Valley, but it was still a great experience.
We booked a tour through a tourist agency for the price of 150 DH (15 EUR). We went in a maxi taxi with only four other tourists, and our driver was also an excellent guide. He stopped whenever we wanted to take pictures, which was awesome. A big part of the trip was just watching the scenery we drove through.