Ruta del Sillar Guide: Añashuayco Quarries & Culebrillas Slot Canyon, Arequipa

Every cathedral tower, convent cloister, and colonial mansion in UNESCO-listed Arequipa owes its existence to a geological cataclysm that occurred roughly 1.65 million years ago, when pyroclastic flows from the Chachani volcanic complex filled the surrounding ravines with thick sheets of lightweight, porous welded volcanic tuff (ignimbrite) known locally as sillar. Fourteen kilometres northwest of the Plaza de Armas in the districts of Cerro Colorado and Uchumayo, the half-day Ruta del Sillar circuit takes you directly into the active quarries and virgin slot canyons where the "White City" was born.

1. Canteras de Añashuayco: 500 Years of Hand-Cut Volcanic Stone

Stretching for more than two kilometres along the arid ravine at the foot of Nevado Chachani, the Canteras de Añashuayco have been worked continuously since the sixteenth century. In 2014, the traditional knowledge and artisanal technique of Arequipa's master sillar cutters (maestros cortadores de sillar) were declared Cultural Heritage of the Nation:

• Watching the Maestros Cortadores at Work: Standing beneath 30-metre-tall vertical white cliffs that glare like snow under the Andean sun, you can watch quarrymen split huge boulders of volcanic rock entirely by hand, without power saws, using only iron wedges (cuñas), flat chisels (cinceles), and heavy sledgehammers (combos) to shape standard rectangular building blocks sold in 200-block lots called a tarea.
• Monumental Sculptures Carved into the Quarry Wall: Over the past decade, the quarrymen's association has transformed the amphitheatre into an open-air sculpture park, carving a full-scale replica of the 1698 Iglesia de la Compañía facade, a colonial birth scene, rearing horses, an Andean condor, and the coat of arms of Arequipa directly out of the living white rock face. Visitors can even try splitting or carving a small piece of sillar under a master mason's guidance.

2. Quebrada de Culebrillas: The Salmon-Pink Slot Canyon & Petroglyphs

Fifteen minutes further west in the Uchumayo district, the second stop on the Ruta del Sillar visits an untouched, unquarried volcanic gorge: the Quebrada de Culebrillas:

• Walking the Pink Ignimbrite Gorge: Carved over millennia by summer flash floods rushing down toward the Chili River, this narrow, sinuous slot canyon winds for nearly a kilometre between 15- to 20-metre-high vertical walls of warm salmon-pink and cream sillar, in places narrowing to just two or three metres across.
• Pre-Inca Petroglyphs & Apachetas: Halfway along the sandy canyon floor, look closely at the lower rock walls to spot pre-Inca Wari and Churajón petroglyphs (circa 600 to 1300 CE) etched with outlines of llamas, foxes, serpents, and solar figures, before emerging at a natural rock amphitheatre crowned by ceremonial stone cairns (apachetas).

3. How to Visit the Ruta del Sillar

Half-day morning or afternoon tours depart daily from the Historic Centre of Arequipa, or you can hire a taxi for a three-hour round trip via the Cerro Colorado road; bring sunglasses, a hat, and sunscreen for the bright quarry walls.