The Volcanic City: How Arequipa Is Made of Misti

Stand in the Plaza de Armas of Arequipa and look up. The arcades on three sides of the square are blindingly white. The Cathedral on the fourth side is white. The Iglesia de la Compañía at the southeast corner is white. The whole historic center, every church and mansion and cloister inside the UNESCO-listed perimeter, is white. The whiteness is not paint. It is the material itself. Now turn south. About thirty kilometers away, weather permitting, you will see a near-perfect cone rising to nearly six thousand meters. That is Misti. It is an active volcano. It last erupted in 1985 and is monitored continuously by the Peruvian Geophysical Institute.

The relationship between those two facts, the white city and the volcano above it, is the city's founding condition.

What sillar is

Sillar is welded volcanic tuff, a rock formed when hot volcanic ash falls in a dense enough layer to compact under its own heat and weight before it cools. The southern Peruvian Andes produced enormous sillar deposits during a series of major eruptions roughly two million years ago. Misti and its neighbors, Chachani to the north and Pichu Pichu to the east, have been depositing additional sillar in smaller quantities ever since. The deposits around Arequipa are quarried in open-air pits to this day. The largest, in the Añashuayco canyon to the west of the city, has been worked continuously since the colonial period.

Three properties matter. First, sillar is light. It is roughly half the density of the granite the Spanish used in Lima or Cusco. Second, sillar is soft enough to cut with a hand saw when freshly quarried, but it hardens on exposure to air over a few weeks. This means an Arequipa stonemason in 1600 could cut a block, carve it, set it in a wall, and the finished wall would be stronger than the freshly cut block had been. Third, sillar is white. Not painted-white; the rock itself is creamy off-white, sometimes with a pink or grey tint depending on the deposit, and reflects sunlight back into your eyes with an intensity that is genuinely physical.

These three properties, light, carveable-then-hardening, brilliantly reflective, produced the city.

How sillar shaped the architecture

Arequipa sits in a seismically active zone. Major earthquakes hit the city in 1582, 1600, 1687, 1784, 1868, and most recently in 2001, when a magnitude eight quake collapsed one of the Cathedral's bell towers. Spanish stone in this climate would have been a problem. The granite blocks of the Cusco Cathedral, dragged from Sacsayhuaman, were heavy enough to amplify their own destructive force in a quake. Sillar's lightness saves Arequipa from much of that.

The carveable-then-hardening property is what produced the Arequipan baroque. A mason working in granite has to plan every cut against the eventual stoneworker's tools. A mason working in sillar can carve directly. The result is the dense, deeply incised foliage and figurework that covers the façade of La Compañía, completed in 1698, and the cloisters and side door of Santa Catalina. The mestizo baroque of Arequipa is what happens when the masonry constraint of European baroque is lifted by a softer material and Andean indigenous artisans get to carve their own iconography into Christian forms. Look at the Compañía façade: you find pomegranates, grape vines, kantuta flowers, Andean cherubs with feline features, all rendered in a depth of relief that no European stonecutter would attempt in granite.

The reflectivity is what gave the city its name. The Spanish chroniclers in the sixteenth century called Arequipa the White City because it looked white from a long way off. Travelers crossing the dry hills from the coast or from Lake Titicaca saw the white sprawl in the bowl below Misti and used the same word. The whiteness was never a metaphor. It was always the rock.

The constraint underneath

A city built next to an active volcano lives in a particular relationship with time. The Cathedral has been destroyed and rebuilt five times by earthquakes, eruptions, or fire. The first version went up in the 1540s. The current Neo-Renaissance façade dates from the late nineteenth century, with the 2001 earthquake repairs visible in the bell-tower masonry. The Iglesia de la Compañía at the corner of the plaza, by contrast, has survived since 1698 because the Jesuits chose a more conservative footprint and lower roofline, and because sillar's lightness made the lateral walls more forgiving in a quake.

A volcanic city accumulates differently from a stable one. The colonial buildings you see today are mostly the third or fourth iteration on the same plot. The continuity is in the plan, not in the fabric. The Plaza de Armas has been on its current footprint since the 1540s; nothing on it is older than the late seventeenth century in continuous material form.

The cultural reading mirrors the geological one. The mestizo baroque of Arequipa is not a foreign style that arrived intact from Spain and was applied to a passive Andean ground. It is the local response to a local constraint: white volcanic stone, indigenous carvers, Spanish patrons, an active volcano, recurrent earthquakes. The constraint never went away. The city adapted around it.

The other Arequipa

The two Roamer walks divide the white city into its two main registers. The White City tour is the public Arequipa: the cathedral, the Plaza de Armas, La Compañía, the church of La Merced, the mestizo façades, the volcanic stone in its civic mode. It is the half of Arequipa that wanted to be seen.

The Santa Catalina tour is the other half. The Monastery of Santa Catalina, founded in 1579, was a Dominican cloister for the daughters of wealthy criollo families. It occupied roughly twenty thousand square meters in the middle of the historic center, surrounded by its own high walls, and was sealed from the outside world for nearly four centuries. Inside the walls is a town: streets named for Spanish cities, painted in deep blue, ochre, and terracotta natural pigments, with private cells where the nuns lived with their personal slaves and held parties. The Vatican broke the relaxed conditions in 1871 and imposed full enclosure. The monastery opened its doors to the public in 1970. The colors and the cells are still there.

Santa Catalina is the inverse of the city outside it. The Plaza de Armas is white, public, civic, masculine in its institutional register. The monastery is colored, private, religious, organized around women's spiritual and economic life. Both are made from the same sillar. The two together describe how a colonial society used the volcano's gift.

What not to romanticize

A city that produces its own building stone from the mountain above it has labor implications. The Añashuayco quarry has been worked, almost continuously, by canteros, stone cutters, who carve blocks by hand in heat that regularly reaches forty degrees Celsius. The work has historically been low-paid and dangerous, and the canteros are mostly migrants from the highlands, descendants of the indigenous communities whose labor built the colonial city. The white façades you walk past in the Plaza de Armas are the visible end of a labor chain that includes the quarry workers, the masons, the carvers, and the indigenous symbolism they smuggled into the Christian iconography. Read the Compañía façade with that chain in mind.

The 1780 Túpac Amaru rebellion, which began in the southern highlands and reached Arequipa as a series of indigenous tax revolts, is the political register of the same labor question. The 1950 general strike in the city, which forced national-level concessions on rural labor protections, is another. Arequipa has a long history of dissent that the brilliant white façades do not advertise. The city's nickname as the "Independent Republic of Arequipa," half-joking, half-serious, points at it.

How to walk

Two tours, three hours, one geological fact. Walk the White City tour first to install the material in your eye. Look hard at the Compañía façade. Stand in the cloisters and run your hand over the relief carving. Notice how soft the stone feels and how confidently it holds the line. Then walk Santa Catalina. Open a door. Step into a courtyard. The sillar walls inside are the same volcanic rock, painted with mineral pigments the nuns mixed themselves. The colors are the part you remember; the rock is what made the colors possible.

Sometime during either walk, look up. If the sky is clear, Misti will be visible. The volcano is the city's source material and its standing threat. The white that surrounds you is what it gave. The earthquakes are what it takes back, occasionally. Five hundred years of this exchange is the city you are walking through.