Sacsayhuamán

Stand close to the wall and look up. Some of these stones are taller than two people. Their edges curve softly, like enormous pillows, and each one meets its neighbors in a perfect seam. Run your eyes along the joints. There is no mortar anywhere, only stone against stone.

This is Sacsayhuamán, a walled complex on a hill above Cusco, at about 3,700 meters above sea level. The name comes from Quechua; one common translation is satisfied falcon. From the esplanade you can see the whole historic center below, its red tile roofs packed around the Plaza de Armas. The Inca considered Cusco the center of their world, and this hill guarded it.

The site is far older than the Inca empire. People of the Killke culture built here from around 1100. When the Inca rose to power, they took over the hill and rebuilt it on an enormous scale. Most scholars credit the emperor Pachacuti with starting the great walls in the fifteenth century.

The main feature is a set of three zigzag terraces, one above another, climbing the hillside like giant steps. The lowest wall runs for roughly 400 meters, and each terrace stands several meters tall. The zigzag was practical. Attackers had to expose their side to defenders at every turn. Some accounts also link the shape to lightning, or to the teeth of a puma.

The largest blocks in the lowest wall are estimated to weigh well over 100 tons. Workers quarried limestone nearby and moved the blocks with ropes, log rollers, earth ramps, and patience. No wheels, no iron tools, no animals strong enough to pull such loads. Chroniclers wrote that tens of thousands of laborers worked here in shifts, as part of the labor tax the empire collected. The work took decades.

How the stones fit so tightly is not a mystery so much as a display of effort. Masons lowered a block against its neighbor, marked the contact points, lifted it away, and chipped at the surface, again and again, until the two faces matched. The result has survived centuries of earthquakes that toppled far newer buildings.

The Spanish called this place a fortress, and it served as one. But many archaeologists now describe it as a ceremonial complex too, a setting for rituals of the sun. On the flat summit once stood three towers, described by chroniclers as tall enough to be seen from far across the valley. You can still trace the round foundations of one of them, called Muyuqmarka.

In 1536, Sacsayhuamán became a battlefield. Manco Inca led a great uprising against the Spanish occupiers of Cusco and used this complex as a stronghold. The fighting was fierce. Juan Pizarro, a brother of the conquistador Francisco Pizarro, died from a wound received during the assault. When the walls fell, the rebellion around Cusco lost its anchor.

After the conquest, the Spanish treated the hill as a quarry. For decades, builders dragged the smaller stones downhill to raise churches and mansions, including parts of Cusco's cathedral. Colonial Cusco was built, quite literally, from the bones of this place. Only the largest blocks were too heavy to move. What you see today is the skeleton that remained.

A tradition passed down in Cusco says the city was laid out in the shape of a puma, the sacred cat of the Andes. In that design, Sacsayhuamán forms the head, and the zigzag walls are its teeth. Historians debate how literally to take this, but the image has stayed with the city for centuries.

Every year on June 24, the esplanade fills for Inti Raymi, the Festival of the Sun. The modern celebration began in 1944, recreating the great solstice ceremony of the Inca court. Hundreds of performers in costume honor the sun before crowds of thousands. For one day, the hill works again as it once did.

Across the grass from the main walls rises a smooth rock outcrop called Suchuna, or the Rodadero. Natural channels in the stone form slides, polished by generations of children, and grooves worn by glaciers long before any builder arrived. Climb it for the wide view back over the zigzag walls.

Walk the top terrace before you go. Below you, Cusco hums with traffic and church bells. Under your hand, the stone is cold and exact. The people who set these blocks left no written records. They left the fit of stone on stone, and that has been enough to keep their work standing.