Cerro Galán

Cerro Galán is not a cone but a caldera, the collapsed remains of an eruption around two million years ago so vast that it ranks among the largest known anywhere, leaving a bowl roughly thirty-five kilometres across on the Catamarca puna. Inside it the ground is a plain of pale ignimbrite at around 4,500 metres, with a resurgent dome pushed up at the centre and a shallow lagoon on the floor where flamingos feed and vicuñas come to drink. The rim is broken and low from inside, so the scale is easier to understand from the approach than from within, and the volume of rock ejected in the original eruption is difficult to picture at all. Reaching it means a long day of driving on unmarked tracks with a guide who knows the route.

What you actually see

• The caldera floor - a vast pale plain at around 4,500 metres.
• The lagoon - shallow water with flamingos inside the crater.
• The resurgent dome - the uplifted centre of the collapsed caldera.
• The vicuñas - herds grazing on the sparse high grassland.

When to go

April to November for firm tracks and settled weather; summer storms make the route impassable. Trips take a full day from Antofagasta de la Sierra and must start early. Wind and cold are severe at this altitude at any time of year.

Honest expectations

The caldera is so large that from inside it can look like an ordinary plain, which disappoints visitors expecting a crater rim. Access is by unmarked track with real risk of getting lost or stuck, so a guide is not optional. At 4,500 metres, altitude sickness is common.

Nearby

Antofagasta de la Sierra is the base; Campo de Piedra Pómez lies on the same circuit.