The National Museum of Anthropology in Mexico City houses a valuable collection of artifacts from hundreds of pre-Hispanic cultures such as the Aztec, Olmec, Teotihuacan, Zapotec, Mixtec and Maya, as well as information on current indigenous groups. The Zocalo, or Plaza de la Constitution, in Mexico City contains remnants of pre-Columbian history under the concrete slabs and buildings from colonial Mexico flanking it such as the National Palace and Metropolitan Cathedral. Xochimilco's canals in Mexico City date back around 700 years and are still used as a quiet boat ride today, with vendors, musicians and photographers occasionally approaching other boats.