Barreal

Barreal in San Juan Province sits at the base of the Andes at 1,650 metres, on the edge of the Pampa del Leoncito — a flat, hard, bone-dry sedimentary plain 60 kilometres long where carrovelismo (land-sailing on three-wheeled vehicles) reaches 100km/h in the wind that blows off the cordillera every afternoon without fail. The plain is also one of the driest locations in the Americas and holds two astronomical observatories operated by the National University of San Juan, and on clear nights — which means almost every night — the Milky Way appears as a solid object rather than a smear. The sky here is classified as one of the darkest in South America.

The Pampa del Leoncito, adjacent to Barreal in the Calingasta Valley, is a tectonic depression of lake sediments at 2,000 metres altitude, bounded by the main Andean cordillera to the west and the Precordillera to the east. The Complejo Astronómico El Leoncito (CASLEO), established in 1983, operates a 2.15-metre Ritchey–Chrétien telescope — the largest in Argentina — at an altitude of 2,552 metres on the Cerro El Leoncito above the valley; a second facility, the Carlos U. Cesco Station, operates on the valley floor. The combination of over 300 clear nights annually, low humidity, minimal light pollution, and altitude makes the Calingasta Valley one of the premier astronomical observation locations in the southern hemisphere. The valley's ancient rock art sites — petroglyphs carved by the Huarpe culture who populated the region before Inca expansion — are accessible on the roads between Barreal and Calingasta.