The Americas

The peoples of the Americas built cities, temples and palaces entirely independently of Europe, Africa and Asia. Their architecture answers the same questions (how to stand, how to span, how to make a place sacred and a ruler visible) with some of the same answers and some quite different ones. It is worth noticing what they did without. There were no draught animals able to haul heavy loads (the llama carries only a small pack), no wheel used for transport, no iron tools and, with a few minor exceptions, no true arch. Everything was cut with stone and harder stone, moved by human effort with ropes, levers, ramps and sledges, and spanned by the beam or the corbel.

Two regions produced the great traditions. In Mesoamerica (central and southern Mexico and the adjoining lands of Central America) a succession of cultures from the Olmec to the Aztec built cities of plazas and stepped platforms. In the Andes of western South America, from the coast of Peru to the high plateau of Bolivia, builders worked in adobe and stone for four thousand years before the Inca empire unified the region in the fifteenth century AD. Both traditions ended as living ones with the Spanish conquests, of Tenochtitlan in 1521 and of the last Inca stronghold in 1572.

Plaza and platform

The fundamental unit of Mesoamerican architecture is not the room but the platform. A city is a set of plazas, each bounded by raised terraces that carry temples, palaces and ball courts. The largest platforms rise in stages into what we call pyramids, but the word misleads. An Egyptian pyramid is a sealed tomb with a point at the top; a Mesoamerican pyramid is a stepped base with a flat summit carrying a small temple, reached by a single steep stair on its principal face. The rites performed there (processions, offerings, sacrifices) were meant to be seen from the plaza below; the stair was a stage.

℟The pyramid is a platform for a temple

Treat the stepped pyramid as a platform whose purpose is to lift a small temple towards the sky, reached by a single steep stair on its principal face; enlarge it by building a new shell over the old.

The platforms were built of rubble and earth held in by retaining walls, faced with cut stone and finished with thick lime plaster, usually painted red. They were rarely built at a single stroke. When a ruler wished to honour a temple, or to outdo a predecessor, he built a new and larger shell over the old one, so that great pyramids often contain several earlier ones nested inside like the layers of an onion. The Templo Mayor of the Aztec capital, Tenochtitlan, grew in seven such phases.

Teotihuacan and the talud-tablero

In the first centuries AD a city arose in the Valley of Mexico that dwarfed every other in the Americas. Teotihuacan was laid out on a grid oriented about 15½° east of north, along a processional way, the Avenue of the Dead, some 2.5 km long, with the Pyramid of the Moon at its northern end and the Pyramid of the Sun, about 225 m square and 65 m high, beside it. Every building, even the course of the river, conformed to the same bearing. The orientation is widely thought to relate to the sunsets on particular days of the calendar, and later peoples revered the ruined city as the place where the gods had created the present world.

℟Lay out the city on a skewed sacred grid

Align the principal avenue and every building of the city to a single bearing (at Teotihuacan about 15½° east of north) so that the whole city shares one orientation with its great pyramids.

The builders of Teotihuacan gave their platforms a distinctive profile: the talud-tablero. Each stage consists of a sloping wall, the talud, surmounted by a vertical panel, the tablero, framed by a projecting border and cantilevered slightly over the slope beneath. The panels were plastered and painted, and on the Temple of the Feathered Serpent they carry great serpent heads carved in the round. Repeated stage after stage, the profile turns a heap of rubble into a stack of crisp horizontal bands of light and shadow. Its prestige carried it wherever Teotihuacan’s influence reached, as far as the Maya cities of Guatemala.

℟Talud and tablero

Build each stage of a platform as a sloping talud surmounted by a vertical tablero: a rectangular panel framed by a projecting border and cantilevered slightly over the slope below; repeat the pair at every stage.

Teotihuacan: tablero taller than talud (often ≈ 1½–2 × its height)

The Maya temple-pyramid

The Maya cities of the southern lowlands (Tikal, Calakmul, Copán, Palenque and many more) reached their height in the Classic period, between about AD 250 and 900. Their temple-pyramids are the most dramatic in Mesoamerica. Temple I at Tikal, built in the 730s over the tomb of the ruler Jasaw Chan K’awiil I, rises in nine steep terraces, each a sloping wall capped by a projecting apron moulding, with inset corners that make every terrace read as a set of separate panels. A single stair climbs the front to a temple of three narrow rooms, one behind another; above them rises a massive roof comb, once modelled in painted stucco with a colossal seated figure of the king.

The Maya also carved and erected stelae in the plazas before their temples: upright slabs bearing portraits of rulers and hieroglyphic texts dated in their Long Count calendar. The city was a history written in stone, and the buildings were its monuments as much as its shelters.

The corbel vault

Maya interiors are few, narrow and tall, and the reason is structural. Maya builders roofed their rooms with the corbelled vault: from the top of each wall, courses of stone step inward, each projecting a little beyond the one below, until the gap between the two sides is narrow enough to be closed by a flat capstone. The stones of a corbel vault stay horizontal. Unlike the voussoirs of an arch they do not lean on one another and do not push sideways, so no buttress is needed; but nothing holds the overhang up except the weight behind it.

Each half of the vault is a cantilever, and it stands only while its centre of gravity lies behind the inner edge of the wall on which it rests. If it moves in front of that edge, the half tips into the room about it. The Maya solved this by building their walls as a strong core of rubble and lime mortar (the hearting), faced with thin, finely cut stones, and carrying that core up well above the springing of the vault, so that its weight far outweighs the overhang. In the model below, turn off the hearting: the courses become single stones cantilevered over the room, and if they are short or the span is wide, the vault overturns.

℟Keep each half of a corbel vault over its wall

In a corbelled vault each course may project only a little beyond the one below, and each overhanging half must have its centre of gravity behind the inner face of its wall; load the tails of the stones with heavy hearting until the capstone is set.

stable if Σ W·x (behind the springing edge) > Σ W·x (in front)

Because each course may step inward only a little, a wider room needs a taller vault and still heavier walls. Maya rooms therefore rarely exceed about three metres in span, however long they are. To make a larger building the Maya added more galleries side by side, as in the Palace at Palenque, whose ranges of parallel vaulted corridors surround a series of courtyards. In many temples the masonry far exceeds the space it encloses. The same logic explains the roof comb: the heavy crest stands over the thickest walls, where its weight also helps to pin the vault halves down.

℟Corbelled rooms are narrow

Keep the span of a corbelled room to about three metres or less and make it long instead of wide; to enlarge a building, add parallel galleries rather than widening them.

Maya room spans ≈ 1.5–3 m; vault rise ≈ 1–1½ × span

In the Puuc hills of Yucatán, in the ninth and tenth centuries, builders developed a new technique of finely cut veneer stones over a concrete-like core, and covered the upper façades of buildings such as the Nunnery Quadrangle at Uxmal with mosaics of carved stone: lattices, step-frets and masks of the rain god. At Chichén Itzá the radial pyramid of El Castillo, with a stair on each of its four sides, represents a new, more international style that looked towards central Mexico.

The Andes before the Inca

Monumental building in the Andes is as old as the pyramids of Egypt. At Caral, in the Supe valley near the coast of Peru, stepped platform mounds of stone and fill with sunken circular plazas before them were built around 2600 BC. At Chavín de Huántar in the highlands (c. 900–200 BC) a stone temple was threaded with narrow galleries leading to a carved cult image. On the high plateau by Lake Titicaca, the builders of Tiwanaku (c. AD 500–1000) cut andesite and sandstone with extraordinary precision, joining blocks with metal cramps poured into I-shaped sockets, and carved the monolithic Gateway of the Sun. On the north coast the Chimú built Chan Chan, an immense city of adobe walled compounds, their walls moulded in relief.

Inca masonry

The Inca rose from a small kingdom around Cuzco to rule, by about 1500, an empire running some 4,000 km along the Andes. Their architecture is remarkably uniform across that territory, and deliberately so: it was one of the instruments of empire. Most buildings are single rectangular rooms with steep thatched roofs, grouped round courtyards inside enclosure walls (the kancha). What makes them extraordinary is their masonry, and a small number of forms repeated everywhere.

Inca walls range from fieldstone laid in clay to the celebrated fine masonry of Cuzco, which comes in two kinds. In polygonal masonry (the great zigzag ramparts of Sacsayhuamán, the street wall of Hatunrumiyoc with its twelve-angled stone) no two blocks are alike and no joint runs straight for long; every block was shaped to fit the ones already laid, lowered, checked, lifted and pounded again until the faces closed without mortar. The chronicler Garcilaso de la Vega, who grew up in Cuzco in the decades after the conquest, marvelled that stones so huge had been fitted so closely without iron tools, draught animals or wheels.

℟Fit every stone to its neighbours

Shape each block of the finest walls to the irregular outline of the stones already laid, grinding the joints until they close without mortar; let the stones be as large and as many-sided as they come.

The other fine kind is coursed ashlar, reserved for the holiest buildings: rectangular blocks laid in perfectly level courses that diminish in height towards the top of the wall. The curved wall of the Coricancha, the temple of the Sun in Cuzco, which now carries the church of Santo Domingo, is the classic example. In both kinds the faces of the stones are left slightly pillowed, so that every joint reads as a crisp line of shadow.

℟Coursed ashlar for the holiest places

For the most sacred buildings lay rectangular blocks in level courses that diminish in height towards the top of the wall, with pillowed faces and joints closed without mortar.

The trapezoid and the batter

Every Inca opening is a trapezoid. Doorways, windows and the rows of niches that line temple walls are narrower at the top than at the bottom, and each is spanned by a single stone lintel. The walls themselves lean inward, a few degrees on each face, so that the wall, the door and the niche all share one inclination. The trapezoid shortens the lintel for a given opening at the foot, and the whole system (low centre of gravity, inclined faces, interlocking blocks) has served well in one of the most earthquake-prone regions on earth. When Cuzco was shaken in 1650 and again in 1950, colonial churches fell while the Inca walls on which they stood survived.

At the entrances to the most important precincts the Inca doubled the frame, setting the trapezoidal door within a second, larger recessed trapezoid: a hierarchy of openings written in the wall, the equivalent of the classical orders that elsewhere mark a door of honour. And beyond the building, the Inca shaped whole landscapes: terraces stepping down mountainsides at Moray and Pisac, royal estates such as Machu Picchu fitted to the living rock, and a road network of some 40,000 km with rope suspension bridges over the gorges.

Two answers to the same questions

Set beside the ancient Old World, the architecture of the Americas is at once familiar and strange. The platform with a temple on top recalls the Mesopotamian ziggurat; the corbel vault recalls Newgrange and Mycenae; the battered wall and the trapezoidal door recall Egypt. None of these were borrowed. They are the answers that stone, human labour and religious ambition give when the arch is unknown and the beam must be short. What is distinctive is the emphasis: Mesoamerica made an architecture of exteriors, platforms and stairs addressed to crowds in plazas; the Andes made an architecture of walls, whose perfection lay in the fit of one stone against the next.