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The Marvels of Ancient Roman Aqueducts

Ancient Roman aqueducts stand as towering symbols of Rome's advanced engineering and architectural prowess.

The Marvels of Ancient Roman Aqueducts
A possible representation of Pont du Gard at its full glory. Illustration: DALL-E

Ancient Roman aqueducts stand as towering symbols of Rome's advanced engineering and architectural prowess. These impressive constructions, designed to transport water over vast distances, played a crucial role in the development and sustenance of the sprawling Roman Empire.

Rome, at its zenith, was a city with a great demand for water, supporting opulent gardens, grand fountains, public baths, and residential amenities like running water and sewage systems. Its industries, thriving on water for machinery and production, served a population between half a million to one million. So aqueducts supplied public baths, latrines, fountains, and private households; they also supported mining operations, milling, farms, and gardens.

That was made achievable by Rome's eleven aqueducts, which were monumental in both technology and architecture, channelling water from the surrounding areas into the city since the first was constructed in 312 B.C.

Rome was known for its extensive public amenities, such as abundant fountains at almost every street corner in Pompeii, requiring a continuous flow of water. Virtually every Roman city boasted public baths, demanding significant volumes of fresh water. For instance, the Baths of Caracalla in Rome had a dedicated aqueduct, the Aqua Marcia, delivering an astonishing 18.5 gallons per second. This supply was stored in a massive cistern divided into 18 sections, holding a total of 80,000 cubic meters, allowing water to circulate through the baths and then drain off into the Tiber via a large underground system.

“Rome’s greatness rested on three wonderful achievements: aqueducts, roads, and the sewage system.”, Diogenes of Halicarnassus

While the concept of aqueducts wasn't a Roman invention—preceded by Assyrian, Greek, Egyptian, and other civilizations—the Roman aqueducts distinguished themselves through their scale and architectural magnificence. Their designs often featured elevated bridges to traverse valleys and urban spaces, with some still operational today, a testament to their enduring legacy over two millennia.

Aqueduct of Segovia
Aqueduct of Segovia and Plaza de la Artillería, Segovia, Spain. Credits: Bernard Gagnon, Creative Commons

 Pliny the Elder, in his Natural History, characterizes Rome’s aqueducts as a “marvel” that was “unsurpassed”. He writes:

“If we only take into consideration the abundant supply of water to the public, for baths, ponds, canals, household purposes, gardens, places in the suburbs, and country houses; and then reflect upon the distances that are traversed, the arches that have been constructed, the mountains that have been pierced, the valleys that have been levelled, we must of necessity admit that there is nothing to be found more worthy of our admiration throughout the whole universe” (1857, 353 to 354).

Design and Construction: Harnessing Gravity

Roman aqueducts were ingeniously designed to utilize gravity, allowing water to flow from mountain springs and lakes down to cities and towns. This required meticulous planning, surveying, and land management to ensure the water moved at an optimal speed—too fast, and it would erode the structures; too slow, and the water would stagnate.

Aqueducts facilitated water transport exclusively through gravitational force, utilizing a gentle downward slope in their stone, brick, concrete, or lead conduits to dictate flow speed. Typically, these channels were underground, adhering to the land's natural contours, avoiding mountains by detour or tunnelling. While the iconic stone arches of aqueducts like the Pont du Gard in France are visible above ground, much of the Roman aqueduct system lay hidden beneath the earth. These subterranean networks, comprising complex tunnels and pipes, ensured the delivery of fresh water to urban centers, with some systems extending underground for the majority of their length.

Pont du Gard
Pont du Gard, in Vers-Pont-du-Gard, Gard department, South France. The Pont du Gard is the most famous part of the Roman aqueduct which carried water from Uzès to Nîmes until roughly the 9th century when maintenance was abandoned. The monument is 49m high and now 275m long (it was 360m when intact) at its top. It's the highest Roman aqueduct, but also one of the best preserved (with the aqueduct of Segovia). The Pont du Gard has been a UNESCO World Heritage site since 1985. Credits: Benh LIEU SONG, CC BY-SA 3.0 DEED

In areas where valleys or low terrains presented obstacles, the aqueducts were supported by bridges, or water was pushed through siphons made of lead, ceramic, or stone under high pressure. To purify the water, sedimentation tanks were often part of the system, trapping debris. Water flow to various destinations was controlled by sluices, distribution tanks (castella aquae), and valves, with excess water directed into cisterns for temporary storage.

“...of all things that have existed in the world, aqueducts are the most marvelous.”, Pliny the Elder

Materials that Lasted Millennia

The durability of Roman aqueducts can be attributed to the materials used in their construction: a combination of stone, brick, and a special volcanic cement called pozzolana. This material, alongside the employment of scaffolding similar to what is used today, contributed to the longevity of these structures.

Aqueduct under construction
A possible representation of an aqueduct under construction. Illustration: DALL-E

Manpower and Maintenance

The construction of Roman aqueducts required significant human labor, often involving slaves for the heavy lifting and digging. Once completed, aqueducts were overseen by a designated official, the ‘Curator Aquarum,’ responsible for their maintenance. Special valves, known as sluice gates, were installed to reroute water in case of pipe damage.

Iconic Aqueducts That Still Impress

Pont du Gard, France: A masterpiece of ancient engineering, the Pont du Gard was built in the first century CE to supply water to Nimes. It is one of the highest and best-preserved Roman aqueducts.

Aqua Virgo, Rome: Integral to Rome's water system since 19 BCE, the Aqua Virgo fed the famous Trevi Fountain and remains operational today.

Aqua Alexandrina, Rome: Constructed between 208 and 235 CE, this aqueduct supplied water to the Baths of Alexander and showcases the ambition of Roman engineering.

Aqua Claudia, Rome: Known for its length and supply capacity, the Aqua Claudia's remnants are visible in Rome's Parco Degli Acquedotti​​.

Valens Aqueduct, Istanbul: This two-tiered construction served as a key water source for the Byzantine and Ottoman Empires, illustrating the extensive reach of Roman engineering​​.

For those who want to learn more about aqueducts, we hope you’ll enjoy this video:

How did Roman Aqueducts work?

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