How were arches built, and who invented them? From Mesopotamian brick to the Roman arch, the Gothic point and the steel arch, with the centering that made them

Architecture · 4 September 2026

An arch is a way of spanning an opening with pieces of material too small to cross it alone, wedge-shaped stones or bricks set in a curve so that each presses on the next and the weight above is carried down the curve to the sides; it stands by compression, which stone and brick bear well, and it pushes outward at its feet, which is the price. The true arch was invented in Mesopotamia and Egypt by about 3000 BC in brick, for drains, tombs and storerooms; the Greeks knew it and hardly used it; the Etruscans built it in stone, and the Romans made it, from the 3rd century BC, the basis of everything they built, aqueducts, bridges, amphitheatres, vaults and domes, on a wooden centering that carried the stones until the keystone was set. The Gothic builders pointed it, the Islamic world curved it into horseshoes and scallops, and the 19th century built it in iron and steel; the Pont du Gard and the Colosseum show the Roman arch at its best. Below: the false arch, who invented the true one, how an arch is built, why it stands, the shapes, the arch in vaults and domes, the great arches, and the myths, with the Roman work in Roman architecture and the Gothic in Gothic architecture.

Before the arch: lintels and corbels

The oldest way to cross a doorway is a lintel, a beam of wood or stone laid across two posts, which works for short spans and breaks if the stone is long, because stone is weak in bending; Stonehenge and the Greek temple are post and lintel, and the Greeks' widest stone spans are about 7 m, with the beams cracking. The corbelled or false arch was the next step: each course of stone projects a little beyond the one below from both sides until they meet, the stones held by the weight of the wall above them rather than by pressing on one another; the "Treasury of Atreus" at Mycenae (1250 BC) is a corbelled dome 13 m across, the Maya built corbelled vaults in every palace and could not make a room wider than about 4 m, and the Lion Gate of Mycenae has a corbelled relieving triangle over its lintel. A corbelled arch can be tall but not wide, and needs a thick wall; the true arch needs neither.

Who invented the true arch

The true arch, of wedge-shaped pieces in compression, appears in mud brick in Mesopotamia and Egypt in the early 3rd millennium BC: brick arches over drains and tombs at Ur and Nippur of about 3000–2500 BC, barrel-vaulted storerooms of the Ramesseum in Egypt of 1250 BC, and the arched gates of Babylon and Nineveh, the Ishtar Gate of 575 BC being a brick arch faced with glazed tile. Brick is small and made in moulds, and a wedge is easy to make; the arch in stone, which needs the wedges cut, came with the Etruscans of Italy in the 6th to 4th centuries BC, whose city gates at Volterra and Perugia are the first monumental stone arches, and the Romans learned it from them. The Greeks knew the arch, built a few in the Hellenistic period, and preferred the lintel for their temples as the proper form; it was the Romans who, having concrete and brick and an empire to build, made the arch the unit of their architecture from about 300 BC: the Cloaca Maxima's arches, the Pons Aemilius of 179 BC, the first stone bridge over the Tiber, the aqueducts, the Colosseum's 240 arches on three storeys, the Basilica of Maxentius's vaults and the Pantheon's dome, all one idea. Arch.

How an arch is built

• Centering. A wooden frame in the shape of the arch's underside, built on the ground or on the piers, is set between the supports; the arch is laid on it, and until the last stone is in place the frame carries everything. The Romans left the ledges (offsets) that carried the centering on the piers of the Pont du Gard, and the holes for its beams.
• Voussoirs. The wedge-shaped stones, cut so that their sides radiate from the centre of the curve, are laid from both sides at once, from the springers at the bottom upward, so that the load on the centering stays balanced.
• Keystone. The last voussoir, at the top, is driven in to lock the ring; it is no more important than the others in the finished arch, but it is the one that completes it, which is why it is decorated.
• Striking the centering. The wedges under the frame are knocked out and the frame lowered gently, so that the arch takes its load gradually and settles; the frame is moved to the next arch. A brick arch is laid the same way, in rings, with the bricks tapered or the joints wedged with mortar.
• Abutments. The arch pushes outward at its feet, and the piers or walls must be heavy enough or braced enough to hold it; a row of arches braces itself, each pushing on the next, and the end arches need heavy abutments, which is why an arcade ends in a mass of wall.
• Extrados and intrados. The outer and inner curves; the spandrel is the wall between the extrados and the horizontal above, the rise the height from the springing to the crown, the span the width.

Why it stands

Each voussoir is squeezed between its neighbours by the weight above, and the squeeze runs along the curve as a line of thrust that, if the arch is well shaped, stays inside the stone all the way down to the supports; stone and brick can bear enormous compression and almost no tension, and the arch is the form that keeps every part in compression. The ideal shape for a load spread evenly is the catenary, the curve of a hanging chain turned upside down, which Hooke stated in 1675 and which Gaudí used with real chains; a round arch carries more of its load at the crown and pushes out more at the feet, a pointed arch carries its thrust more steeply and pushes out less, which is why the Gothic could build higher on thinner walls, and a flat arch, a lintel of wedges, pushes out most of all. Hanging a weight on an arch does not break it; pulling its feet apart does, and every collapsed arch in history fell because its supports moved.

The shapes and when they were used

• Semicircular. Rome, Romanesque, the Renaissance; the rise is half the span, and the arch is set out with a compass.
• Segmental. Less than a semicircle, flatter, pushing outward more; Roman bridges, Chinese bridges, Georgian windows.
• Pointed. Two arcs meeting at a point, from Sasanian Persia and the Islamic world, into Europe by 1100 and the mark of Gothic; equilateral, lancet and drop variants by the ratio of the arcs.
• Horseshoe. More than a semicircle, closing in at the feet, Visigothic and then the arch of Islamic Spain, Córdoba's mosque.
• Ogee. An S-curve on each side meeting at a point, from Islamic and Indian architecture into Venice and English Decorated Gothic of the 14th century.
• Tudor. A flattened four-centred arch, the English arch of 1500, on Hampton Court.
• Elliptical and basket-handle. Three-centred arches of the Renaissance and Baroque, flatter than a semicircle, for bridges.
• Parabolic and catenary. Gaudí's arches and the Gateway Arch, the shapes of pure compression.
• Flat or jack arch. Wedges in a straight line over a window, a lintel that is really an arch; Georgian and Victorian brick houses.

Vaults, domes and bridges

An arch extended in depth is a barrel vault; two crossing are a groin vault; an arch rotated is a dome; and every roof of stone from the Roman baths to Chartres is an arch in one of these forms, with the thrust handled by thick walls, by buttresses, or by the flying buttress. A bridge is an arch or a row of them over water, which the Romans built in stone to spans of 30 m, the Chinese, at the Zhaozhou Bridge of 605, in a segmental arch of 37 m with open spandrels a thousand years before Europe, the medieval builders in pointed arches with cutwaters, and the 18th century, at Pontypridd in 1756, to 43 m; the iron arch of Coalbrookdale of 1779 began the metal bridge, the steel arch of the Eads Bridge at St Louis in 1874 spanned 158 m, the Hell Gate in New York in 1916 298 m, the Sydney Harbour Bridge in 1932 503 m, and the Chaotianmen Bridge at Chongqing in 2009 552 m. The Gateway Arch in St Louis, of 1965, 192 m high and wide, is a catenary of steel with concrete inside, and the largest arch that is only an arch.

The great arches

• Colosseum, Rome (AD 80). 240 arches in three tiers of 80, the Roman arch as a whole building.
• Pont du Gard (AD 50). 52 arches in three tiers, the top ones small, laid dry.
• Arch of Constantine (315) and the triumphal arches from Titus to the Arc de Triomphe of 1836 and the Washington Square Arch: the arch as monument, carrying nothing but its own meaning.
• Taq Kasra, Ctesiphon (6th century). The Sasanian palace hall, a brick pointed vault 37 m wide and 37 m high, the largest single-span brick vault in the world, standing in Iraq.
• Great Mosque of Córdoba (785). 850 columns under double horseshoe arches in red and white.
• Zhaozhou Bridge (605). The oldest open-spandrel segmental arch bridge, still in use.
• Chartres, Amiens, Beauvais. The pointed arch taken to 48 m.
• Gateway Arch, St Louis (1965). Eero Saarinen's catenary, 192 m, the arch as the American monument.

Versions and theories

• The Romans invented the arch. The Mesopotamians and Egyptians did, in brick, 2,500 years earlier; the Etruscans made it in stone; the Romans made it the basis of a civilisation, which is why it is called the Roman arch.
• The keystone holds the arch up. Every voussoir does; the keystone is the last in and the one that completes the ring, and the arch cannot stand without it, but no more than without any other.
• The Maya had the arch. The corbelled false arch, which limited their rooms to 4 m; the true arch reached the Americas with the Spanish.
• The Greeks did not know the arch. They knew it and did not like it; a few Hellenistic arches exist, and Greek engineers in Roman service built thousands.
• The pointed arch was invented by the Gothic. It came from Persia and Islam, through Sicily, Spain and the Crusades, and Durham used it in 1093; the Gothic made it a system.
• Arches are stronger than beams. For stone, yes, since stone is strong in compression and weak in bending; for steel and reinforced concrete, which bear tension, the beam came back, and the arch became a choice rather than a necessity.

The vaults and domes that grew from the arch are in who built the Pantheon and what is a flying buttress.

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