🇦🇷 Argentina · Cuyo
San Agustín del Valle Fértil, the main town of the Valle Fértil department, is a green oasis in the arid east of San Juan, a quiet town of hills, a reservoir and shady trees that works as the main base for visiting the famous Ischigualasto Provincial Park (the Valle de la Luna), a World Heritage Site. Its name says it all: in the middle of San Juan's dryness, this is a valley of unexpected fertility.
The town, ringed by the Sierras Pampeanas, offers a placid atmosphere of tree-lined streets, a reservoir for cooling off and a good starting point for exploring the region. A few kilometers away opens Ischigualasto, one of the most important palaeontological sites in the world, where some of the oldest dinosaurs on the planet were found, and beyond it Talampaya, in La Rioja, with which it forms a pair of unmissable parks.
This guide covers the essentials of Valle Fértil: the town of San Agustín and its hill surroundings, the San Agustín reservoir, the crafts and local life, and above all how to organize the visit to Ischigualasto from here and, if you have time, to Talampaya. A destination that combines the calm of a hill oasis with the closeness of one of Argentina's great natural and palaeontological treasures.
Valle Fértil is a hill oasis in eastern San Juan, inhabited since pre-Hispanic times and settled in the colonial period for its water and its fertile land, rare in the region. The main town, San Agustín, grew as a farming village and is today the base for tourism to Ischigualasto, the Valle de la Luna, one of the oldest dinosaur sites in the world and a World Heritage Site.
Read the full history ↓The province of sun and wine in the heart of Cuyo: Huarpe land, birthplace of Sarmiento, rebuilt after the devastating earthquake of 1944, of Syrah wineries, high cordillera and the lunar landscape of Ischigualasto.
Read the history of San Juan →No exact prices: a scale from $ (budget) to $$$$$ (luxury), with 2-3 options per category.
Origins, formation and what the sources say.
In the late 1950s a muleteer and tracker from Valle Fértil named Victorino Herrera guided a group of scientists through the grey badlands of Ischigualasto, that desolate spot locals avoided and the world now knows as the Valle de la Luna. Herrera knew every gully in the terrain and knew where 'stone bones' came to the surface. He took them straight to them. Among the remains he helped find was a predator more than 230 million years old, one of the oldest dinosaurs ever discovered. When the palaeontologist Osvaldo Reig described it scientifically in 1963, he did something unusual: instead of honoring a colleague or a patron, he named the animal after the muleteer. So a goat herder from eastern San Juan was immortalised in palaeontology textbooks all over the planet: Herrerasaurus ischigualastensis.
That anecdote sums up the curious fate of Valle Fértil: a remote hill oasis, founded in the 18th century to grow wheat and raise livestock, that ended up as the gateway to one of the most important scientific windows in the world — the only place on the planet where you can read, layer by layer, the complete chapter of the Triassic in which the dinosaurs were born.
The name says it all: in the middle of the arid east of San Juan, this valley in the Sierras Pampeanas has water, wet meadows and workable land — a rarity that drew people here from remote times. Its pre-Hispanic inhabitants were the Yacampis, a people whom archaeological and linguistic evidence links to the Diaguita of the northwest. They lived from irrigated farming, hunting and gathering carob pods, and left their traces across the valley: mortars hollowed out of the bedrock for grinding seeds, petroglyphs and the remains of settlements in the hill gorges.
The first Spaniards reached the region around 1596, and with them the religious orders: first the Dominicans and, from 1611, the Jesuit missionaries, who settled to evangelise the native population. For almost two centuries, however, the valley remained a marginal territory of the Cuyo corregimiento — which, curiously, depended on Chile until the Viceroyalty of the Río de la Plata was created in 1776 — with people scattered across livestock outposts and no formal town to organize them. That founding would come only at the end of the 18th century, and by administrative decision rather than spontaneously.
On 4 April 1788, on instruction from the town council of San Juan de la Frontera, the field marshal Pedro Pablo de Quiroga founded the Villa de San Agustín de Jáuregui with some 150 settlers. The name honored Agustín de Jáuregui, who had been viceroy of Peru, and the layout followed the colonial manual: square, church, plots shared out among the Spanish families and the valley's Indigenous people relocated near the church for their evangelisation. So was born the town everyone now simply calls San Agustín, the seat of the Valle Fértil department.
Through the 19th century and much of the 20th, the town lived off the land and off relative solitude. Its people grew wheat and maize on irrigated land, raised goats and cattle in the hills, and worked small mines in the Sierra de la Huerta and Valle Fértil, in a subsistence economy shaped by distance: San Agustín is 250 km from the San Juan capital, and the roads were rough well into the 20th century. That isolation, an economic sentence for generations, ended up preserving two treasures: the serene oasis-town atmosphere travelers fall for today, and a stretch of untouched badlands to the northeast that locals called Ischigualasto.
Locals in Valle Fértil always knew there were 'stone bones' at Ischigualasto, but science was slow to arrive. The turning point was 1958, when the palaeontologist Alfred Romer of Harvard University — one of the world's leading authorities on fossil vertebrates — visited the basin and was astounded: he recognized at once that those grey and reddish layers held an exceptional record of the Triassic. His enthusiasm stirred the pride (and the reaction) of Argentine science: over the following years, expeditions from the Museo de La Plata and the Instituto Lillo in Tucumán, with Osvaldo Reig and later José Bonaparte among their leading figures, systematically excavated the site.
The results were extraordinary. Guided by trackers such as Victorino Herrera, the remains of Herrerasaurus appeared, described by Reig in 1963, along with other reptiles from the dawn of the age of dinosaurs. What makes Ischigualasto unique is not only the age of its fossils — more than 230 million years — but their continuity: it is the only place in the world where the Triassic sedimentary sequence is exposed complete and in order, with the exact transition in which the dinosaurs, then small and marginal animals, began to take over the planet. For palaeontologists it is the equivalent of finding the original manuscript of a whole chapter in the history of life.
Definitive fame came in two waves. In 1988 a joint Argentine-American expedition with Paul Sereno and Fernando Novas found the first Herrerasaurus skeleton with a complete skull, a cover-of-the-journal discovery. And in 1991, during a campaign by the Universidad Nacional de San Juan and the University of Chicago, the San Juan palaeontologist Ricardo Martínez lifted from the ground a rock holding the almost perfect skeleton of a primitive dinosaur the size of a large hen. Described in 1993, it was named Eoraptor lunensis: 'the dawn thief of the Valley of the Moon'. For years it was considered the oldest known dinosaur, and it remains a celebrity of documentaries about the origin of the dinosaurs.
The seal came in 2000, when UNESCO declared the 'Ischigualasto–Talampaya Natural Parks' a World Heritage Site, some 275,000 hectares shared between San Juan and La Rioja, for their continental Triassic fossil record, unique in the world, and their desert landscapes sculpted by erosion: el Hongo, la Cancha de Bochas, el Submarino, the red walls of the La Rioja canyon. That 'worthless' spot the valley people avoided became the engine of the region.
International recognition transformed San Agustín del Valle Fértil without taking away its soul. The old farming town of 1788 is now the natural tourist base for Ischigualasto: every morning cars and excursions leave its guesthouses and cabins for the park, about 75 km away, and many travelers put together the combined day with Talampaya from here. The local economy blends that growing tourism with the activities of always — irrigated farming, goat herding that puts kid goat at the center of the regional table, loom weaving and basketry.
But Valle Fértil is not only a base camp. The San Agustín reservoir, right beside the town, is the area's natural swimming pool: a sheet of water among the hills where people swim, fish and paddle, a double blessing in a department where summer bites. The Sierras Pampeanas offer viewpoints and short walks with views of the contrast that defines the place: the intense green of the oasis set against endless dryness. And the sky, far from any light pollution, gives starry nights that rival the rock formations in the park. Travellers who come for the dinosaurs usually leave with another image: a hill town that has spent more than two centuries cultivating its fertile valley with a patience not even world fame could hurry.