Chefchaouen – or Chaouen, as it is often called by Moroccans. The city was founded in 1471as a small casbah (fortress). Chefchaouen's blue walls are a popular subject of interest. It is often called 'The Pearl' of Morocco. There are several theories as to why the walls were painted blue. One popular theory is that the blue keeps mosquitos away, another is that Jews introduced the blue when they took refuge from Hitler in the 1930s. The blue is said to symbolize the sky and heaven, and serve as a reminder to lead a spiritual life.