Juan de Garay laid out Santa Fe la Vieja in 1573 as a link in a chain, a waypoint binding Asunción del Paraguay to the Río de la Plata and the silver of Peru. He built it in the country of the Calchines, Mocoretáes, and Colastinés, on the banks of the Cayastá, and for a colonial outpost it was remarkably orderly, a planned grid of churches, a cabildo, and homes raised from rammed earth under tile roofs. But the location fought back. Cyclical floods gnawed at the settlement, and the native peoples whose land it occupied resisted the intrusion. By around 1660 the colonists relocated the whole city to its present site, the modern provincial capital. The old town was simply left behind, and the river closed over it like a page turning.

For centuries Santa Fe la Vieja was little more than a name and a guess. Then in 1949 the researcher Agustín Zapata Gollán began to dig, and the lost city came up out of the dirt: the original street plan, the rammed-earth walls of churches dedicated to San Francisco, Santo Domingo, and La Merced, the cabildo, and the houses of the first settlers. The excavation recovered not just structures but the texture of early colonial life on the Argentine littoral. Today the ruins form the Santa Fe la Vieja Archaeological Park and the Juan de Garay Ethnographic and Colonial Museum, and the site has been declared a National Historic Monument, a rare instance of a founding city that can be visited where it actually began.

Even the word Cayastá carries the theme of departure. It first appears in a document from 1607, and the engineer Augusto Fernández Díaz traced it to Kollastas, a fusion of Kolla and Astay, a term that denotes moving, so that Cayastá would mean something like "the Kolla people who move on." The Kolla were one of the Aymara-speaking peoples, a nation with its own dialect that fell under Inca dominion far to the northwest. How that name traveled all the way down to a bend in the Paraná is its own small mystery, a thread connecting the high Andes to the wet lowlands, language outlasting the people who first spoke it here.

Modern Cayastá is a comuna of about 3,367 people, an unremarkable riverside town in Santa Fe Province that happens to sit beside one of the most significant archaeological sites in Argentina. In 1742 it served as a Mocoví reduction, one of the mission settlements where the church gathered indigenous communities, another layer in a place already thick with them. The everyday life of the town goes on quietly above the foundations of the country's first planned city. Visitors come to walk the recovered grid of Santa Fe la Vieja, to stand in the outlines of churches raised by hand more than four centuries ago, and to see the artifacts gathered in the Juan de Garay museum. There is a particular kind of weight in a place like this, where the colonial, the indigenous, and the modern are stacked within walking distance, and the ordinary present unfolds, unbothered, on top of the extraordinary past.