How Ancient Volcanic Ash and Ice Sculpted a Surreal Peruvian Stone Forest

Countries & Cities · Published 30 September 2026 Swipe more like this →

In short: High in the Peruvian Andes, the Huayllay National Sanctuary features a landscape of bizarre, towering rock formations. Known as the Bosque de Rocas, this high-altitude plateau was shaped not by human hands, but by a violent volcanic past followed by millennia of relentless glacial erosion. It is a geological masterpiece.

Located within the Meseta of Bombón in the Pasco Region, the Huayllay National Sanctuary is defined by its dramatic rock forest. These formations originated at the dawn of the Cenozoic era, when intense volcanic activity blanketed the region in layers of ignimbrite. This porous volcanic ash settled over older foundations of limestone, sandstone, and conglomerate, creating a vast, elevated plateau that would eventually become a canvas for nature’s artistry.

The surreal shapes visible today are the result of extreme environmental forces. Roughly two decades of millennia ago, during the peak of the last ice age, the plateau experienced a punishing cycle of temperature fluctuations. As snow accumulated and melted, water seeped into the porous ignimbrite, freezing and expanding within the fissures. This repeated process of ice wedging fractured the rock, causing massive sections to crumble and leaving behind the intricate, eroded spires that define the sanctuary today.

This unique geological site is frequently compared to other world-famous eroded landscapes, such as the Garden of the Gods in the United States and the Shilin Stone Forest in China. Beyond its scientific intrigue, the sanctuary has become a premier destination for hikers and international rock climbers. Visitors navigating the area must contend with a harsh, arid climate, where temperatures can swing wildly from a high of 13.8 degrees Celsius down to a freezing -8 degrees Celsius.

Spanning a district surface area of 607 square kilometers, the sanctuary serves as a testament to the power of geological time. While the rock forest remains the primary draw, the region also supports native flora and fauna adapted to these cold, high-altitude conditions. It stands as a protected natural wonder, offering a rare glimpse into the transformative power of volcanic deposition and glacial weathering on the Andean landscape.

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