Mardones Valley is a short and low valley that reaches a maximum elevation at Paso Bermejo at around 4500m. It can be hiked, out and back, in one strenuous day, but it is not recommended. During the winter the valley is used primarily for heliskiing by nearby Portillo Ski Resort, winter military exercises, and randonee circuits. Elevation change for skiing is on average 1500 meters. Alternatively, there is access from the international highway which the nearby School for High-Mountain Training of the Chilean military uses for winter hiking and randonee.
When hiking in the summer months, one should start from Los Hornitos (2300m). After breaking north from the old mining road there is an initially steep ascent (300m) of about an hour. Upon cresting the rise, which permits views both north and south, the Mardones Valley comes into its own.
Scramble up the boulders on the south face for another 400 m elevation jump and an even higher perspective on Juncal and view to the North and South. Or, rise gently past multicolored streams, in aqua wintergreen, ochre and yellow as they rush from heavily mineraled mountain slopes. Don’t drink that water. Condors nest nearby on the steep north valley slopes, and barely tame horses freeze as one walks by, with their hind legs cocked in defensive anticipation. Farther in, the valley opens up to flat green pastures fed by underground streams of water that occasionally bubble up to the surface. Wreckage from a long ago helicopter accident further color the landscape. A high ledge in the distance beckons mountains climbers to challenge, and to the north a steep curving ascent is promising. Maybe there is a high pass to a minor valley. It has never been tried before.
As you follow the Mardones, now a stream, to the East one ascends steadily towards the main pass of 4250m. To your left the rocky gray ground has exploded in a rainbow of different colors and a spring has stimulated a patch of bright green grass. Further on, rocks are white and yellow and the water splashes down to the valley floor. Another hour to reach the pass and the tallest mountain in South America, the heavily glaciered Mt. Aconcagua, is directly in front of you. A halo of clouds surrounds it, seemingly even with the brightest sun or bluest of skies. In the foreground is the statue of Christ the Redeemer, el Cristo Redentor, perched upon the border with Argentina and sign of good relations with Chile. Far below is the international road that would lead you car to the border with Argentina.
Underfoot, soft pebbly dirt, a welcome respite from the otherwise harsh conditions, seems to have been raked to perfection by some sort of groundskeeper and is damp from still melting snow.
Now in the setting sun to your campsite at the valley floor below, with an eye on Juncal directly ahead of you. One perks up to hear the loud braying of a distant pair of guanacos as they bound amazingly up rocky slopes that would have taken you an hour in ascent.
At camp you are surrounded by peaks of varying magnitude and small flowers and grasses make the air smell sweet.