The tianguis was the periodic Mesoamerican marketplace, an organised civic institution rather than ad hoc trade. The greatest, at Tlatelolco beside Tenochtitlan, drew tens of thousands of people daily into a regulated plaza where goods were laid out by type, prices and measures were policed, and a market court settled disputes on the spot. Spanish eyewitnesses compared its scale and order to the largest markets of Europe. Smaller tianguis on fixed-day cycles knitted the wider valley into a single exchange system.
It establishes a sophisticated, planned commercial urbanism in the pre-Columbian Americas, with dedicated market plazas as a core civic land use. The institution and its name survive in Mexican cities today.