MEXICO CITY - JANUARY 17:  Aztec shaman performing a spiritual cleansing ritual in the Zocalo on January 17, 2009 in Mexico City, Mexico. With an estimated population of more that 22 million inhabitants, Mexico City is one of the largest cities in the world. It is the heart of Mexico´s historical and cultural heritage, and at the same time is a city rapidly progressing into the 21st century.  (Photo by Nina Raingold/Getty Images)