Huilo-Huilo Biological Reserve

[2] The reserve was created in 1999 and includes 600 km2 (232 sq mi) of native forest in Chile dedicated to wildlife conservation and tourism.

The reserve is owned by the businessman Víctor Petermann who bought it in the 1990s during land sale program of the late Pinochet dictatorship.

The main entrance is on the international gravel road that connects Panguipulli with San Martín de los Andes, Argentina.

In order to reach San Martín de los Andes from the west, one must travel through the Hua Hum Pass.

After leaving Chile route 203 in Puerto Fuy, one must board the Barcaza Hua Hum a ferry that crosses Pirihueico Lake in approximately 90 minutes.

After crossing Pirihueico Lake, the ferry arrives at Pirihueico, the last Chilean outpost before the Hua Hum Pass and eventually Ruta 4 in Argentina The nearest town to Huilo-Huilo is Neltume, the site of a 1981 violent episode between members of MIR, and members of the military dictatorship in Chile.

Contact between the water of the aquifer and magma may have caused the explosive phreatic eruptions, that created the Tumba del Buey (bull's tomb) crater on the western flank of the volcano.