Ischigualasto is a desert basin in the north-east of San Juan province that happens to contain one of the most complete records anywhere of the Triassic, the period when the first dinosaurs appeared. Eoraptor and Herrerasaurus, among the earliest dinosaurs known, were both found here. Together with Talampaya just over the La Rioja border, it is a UNESCO World Heritage Site.
Most people know it as the Valle de la Luna — the moon valley — and the landscape earns the name: grey and white clay badlands, red cliffs, and rock formations carved by wind into shapes that have acquired names. El Submarino is a free-standing tower that does look like a conning tower. La Cancha de Bochas is a field of near-perfect stone spheres, concretions weathered out of the rock, scattered like a game abandoned mid-play.
Visits follow a set route of about forty kilometres, in your own vehicle but in convoy behind a ranger, with stops at the main formations — about three hours. There are also bike tours and full-moon night visits, which suit the place's name. The small visitor centre has fossil displays that make sense of what you are looking at.
The nearest town is San Agustín de Valle Fértil, about 75 kilometres away, and San Juan is four hours south. Summer afternoons are extremely hot; start early.