The Genius Engineering of Roman Aqueducts

We tend to think of the Roman Empire as hav­ing fall­en around 476 AD, but had things gone a lit­tle dif­fer­ent­ly, it could have come to its end much ear­li­er — before it tech­ni­cal­ly began, in fact. In the year 44 BC, for instance, the assas­si­na­tion of Julius Cae­sar and the civ­il wars rag­ing across its ter­ri­to­ries made it seem as if the founder­ing Roman Repub­lic was about to go down and take Roman civ­i­liza­tion with it. It fell to one man to ensure that civ­i­liza­tion’s con­ti­nu­ity: “His name was Octa­vian, and he was Caesar’s adopt­ed son,” says sci­ence reporter Car­olyn Beans in the new Cod­ed Cham­bers video above. “At first, no one expect­ed much from him,” but when he took con­trol, he set about rebuild­ing the empire “city by city” before it had offi­cial­ly been declared one.

This ambi­tious project of restora­tion neces­si­tat­ed an equal­ly ambi­tious shoring up of infra­struc­ture, no sin­gle exam­ple of which more clear­ly rep­re­sents Roman engi­neer­ing prowess than the empire’s aque­ducts.

Using as an exam­ple the sys­tem that fed the city of Nemausus, or mod­ern-day Nîmes, Beans explains all that went into their con­struc­tion over great lengths of chal­leng­ing ter­rain — no stage of which, of course, ben­e­fit­ed from mod­ern con­struc­tion tech­niques — with the help of Uni­ver­si­ty of Texas at Austin clas­si­cal archae­ol­o­gy pro­fes­sor Rabun Tay­lor. The most basic task for Rome’s engi­neers was to deter­mine the prop­er slope of the aque­duc­t’s chan­nels: too steep, and the flow­ing water could cause dam­age; too flat, and it could stop before reach­ing its des­ti­na­tion.

Sur­vey­ing the prospec­tive aque­duc­t’s route involved such ancient tools as the diop­tra (used to estab­lish direc­tion and dis­tance over long stretch­es of land), the gro­ma (for straight lines and right angles between check­points), and the choro­bates (to check if a sur­face was lev­el). Then con­struc­tion could begin on a net­work of under­ground tun­nels called cuni­culi. Where dig­ging them proved unfea­si­ble, up went arcades, some of which — like the Pont du Gard in south­ern France, seen in the video — still stand today. They do so thanks in large part to their lime­stone bricks hav­ing been arranged into arch­es, whose geom­e­try directs ten­sion in a way that allows the stone to sup­port itself, with no mason­ry required. When water began run­ning through an aque­duct and into the city, it would then be dis­trib­uted to the gar­dens, foun­tains, ther­mae, and else­where — through con­duit pipes that hap­pened to be made of lead, but then, even the most bril­liant Roman engi­neers could­n’t fore­see every prob­lem.

Relat­ed Con­tent:

How Did Roman Aque­ducts Work?: The Most Impres­sive Achieve­ment of Ancient Rome’s Infra­struc­ture, Explained

The Advanced Tech­nol­o­gy of Ancient Rome: Auto­mat­ic Doors, Water Clocks, Vend­ing Machines & More

Built to Last: How Ancient Roman Bridges Can Still With­stand the Weight of Mod­ern Cars & Trucks

The Amaz­ing Engi­neer­ing of Roman Baths

The Mys­tery Final­ly Solved: Why Has Roman Con­crete Been So Durable?

Based in Seoul, Col­in Marshall writes and broad­casts on cities, lan­guage, and cul­ture. His projects include the Sub­stack newslet­ter Books on Cities and the book The State­less City: a Walk through 21st-Cen­tu­ry Los Ange­les. Fol­low him on the social net­work for­mer­ly known as Twit­ter at @colinmarshall.