the Gallinas River at its confluence with the Tampaon, Tamul Falls cascade into the Tampaon River. Twenty five miles downstream from the falls, the Tampaon meanders past the ancient pyramid site of Tamtoc. Archaeologists believe that Tamtoc is the northernmost pre-Columbian city with pyramids in Mexico, and some speculate that it could be the place of origin of the Aztecs from which they launched their migration to the Valley of Mexico. The best time to visit the waterfall is during the low water season from July to October, when it is easily accessible. Tancanhuitz de Santos This town is located from Ciudad Valles. The Huehuetlan Sierra creek is located here, which is a natural frontier that divides the huastecas to the south and the nahuatlacos native groups. These two indigenous groups nowadays still preserve their languages, dress and customs from their ancestors. When going down from their communities towards the "tianguis" (street market) every Sunday, women wear their quetzquemaletls (v.-shaped ponchos) that they knit and embroider. The languages spoken here mix Nahuatl, Huasteco and Spanish. References External links Municipio de Ciudad Valles Official website Link to tables of population data from Census of 2005 INEGI: Instituto Nacional de Estadística, Geografía e Informática San Luis Potosí Enciclopedia de los Municipios de México Populated places in San Luis Potosí Huastec sites