El Leoncito National Park, National park in Calingasta Department, Argentina

El Leoncito National Park covers 89,706 hectares on the western slopes of the Sierra del Tontal in Calingasta Department, San Juan Province, 34 km from Barreal. A 20 km stretch of National Route 149 crosses it. The terrain rises from the valley floor to the Andean foothills, with dark gray, brown and purple rock ridges and low shrubs.

The area became a nature reserve in 1994 and gained national park status in 2002 when San Juan Province transferred it to federal control under Law 25656. This two-step process reflected growing efforts to protect the region.

The park protects a stretch of the Inca road system (Qhapaq Ñan) that crossed this Andean pass, and the historic casco of the Estancia El Leoncito is preserved within its bounds. The green sign at the entrance marks the turn to the observatories, CASLEO 17 km on, while a black sign reads Parque El Leoncito and Observatorio Astronómico.

The only authorized entrance lies near the Leoncito stream, on the road linking to National Route 149, which crosses the park for 20 km between Barreal and Uspallata. The park has almost no tourist infrastructure, so stock up before arriving. Free camping is available with a stove, tables, grills, toilets and hot showers.

The park enjoys exceptionally clear skies with over 300 clear nights each year, making it highly suited for astronomical observation. Two major observatories operate here and use these ideal conditions for international research and sky studies.