 The organization and function of most city tianguis are mostly the same as those in rural areas; however merchandise varies somewhat and there are problems associated with holding this type of event in the more crowded city.One of the oldest continually operating tianguis in Mexico is the one in Cuautitlán, just outside Mexico City, which has been going on every Tuesday for over 500 years.The market was established in 1491 by the Chichimecas when this area was rural and a way station between Mexico City and points north.