East of the popular Cerro El Plomo (5,424m; 33°14'10"S, 70°12'51"W), near Santiago, El Cajón del Esmeralda stands out immediately for the rugged beauty for which the Central Andes are known: threatening (and threatened) glaciers, imposing rock faces, massive moraines, and steep river valleys. Since the area does not reach great altitude, the landscape is decorated with colorful shrubs and flora. Being hidden from view by Cerro El Plomo, the area has remained mostly ignored by mountaineers.

On November 1, David Cossio, Agustín Ferrer, Catalina Medina, Emil Stefani, and I (all members of Club Andino Universitario) made the first known ascent of Morro de los Castaños (4,736m; 33°14'24"S, 70°11'3"W). We started from Alfalfal on October 29, approaching via the Río Olivares, and then traveled west up the scarcely explored Estero Esmeralda. We made our base camp at 3,100m and bivouacked again at 3,900m. From the bivy, we ascended by a short and easy couloir on the west face. The final step to the summit required us to cross a narrow and exposed ridge, but it didn't require the use of ropes (1,600m, F).

For lovers of the unexplored, this area has several more interesting challenges. The steep, unclimbed south face of Cerro Chávez (4,830m; 33°11'6"S, 70°10'41"W) offers incredible, varied lines up to 500m, and its lower wall holds several ice cascades. The upper east face of Cerro El Plomo presents numerous steep snow and ice gullies up to 600m. Cerro El Plomo’s southeast face was only just recently climbed by Carlos Fouilloux and Nicolás García-Huidobro, in December 2021, over a five-day trip (1,700m, D+ 40–70°); they followed the snake-like Glaciar Castaños to the top. The Sierra Esmeralda and the hills to the east of Morro de los Castaños offer unclimbed peaks and new routes as well, including rocky Cerro Esmeralda Central (4,520m; 33°12'21"S, 70°8'20"W). The slopes of the unnamed hill just east of Morro de los Castaños could also be skied in a good winter.

— Damir Mandakovic, Chile