Ibn Battutah was just 21 when he set out in 1325 from his native Tangier on a pilgrimage to Mecca. He did not return to Morocco for another 29 years, traveling instead through more than 40 countries on the modern map, covering 75,000 miles and getting as far north as the Volga, as far east as China, and as far south as Tanzania. He wrote of his travels, and comes across as a superb ethnographer…