Photo taken on Dec 19, 2013 shows the Koutoubia Mosque, the largest mosque in Marrakesh, Morocco. Located to the north of the foothills of the snow-capped Atlas Mountains, Marrakesh is the most important of Morocco's four former imperial cities. Now it is one of the busiest cities in Africa and serves as a major economic center and tourist destination. The red walls of the city and various buildings constructed in red sandstone give the city the nickname of the "Red City". In 1985, UNESCO declared the old town area of Marrakesh a UNESCO World Heritage Site. [Photo/Xinhua]