Aqua Claudia

By the Editors of the Madain Project

Aqua Claudia, literally meaning "the Claudian water", was one of the four great aqueducts that supplied water to ancient Rome. The Aqua Claudia was one of the two aqueducts, other being the Aqua Anio Novus, that were begun by Emperor Caligula (reigned 37–41 CE) in 38 CE and finished by Emperor Claudius (reigned 41–54 CE) in 52 CE. It was the eighth aqueduct to supply Rome and together with Aqua Anio Novus, Aqua Anio Vetus and Aqua Marcia, it is regarded as one of the "four great aqueducts of Rome".

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Overview

The ancient Roman Empire is renowned for its impressive achievements, notably its extensive aqueduct system. Among these, the Aqua Claudia stands out as a remarkable feat of engineering. At the time of its completion, it accounted for approximately one-fifth of the ancient city's total water supply. Today, nearly two millennia later, significant sections of the Aqua Claudia remain standing, with the viaduct traversing the Park of the Aqueducts (Parco degli Acquedotti) in modern-day Rome being among the most well-preserved. This towering structure, reaching heights of 90 feet at some points, serves as a testament to Rome's engineering prowess and continues to attract numerous visitors.

The longevity of the Aqua Claudia can be attributed to the advanced construction techniques and durable materials employed by Roman engineers. The use of high-quality pozzolanic concrete, known for its hydraulic properties, and meticulous stone masonry contributed to the aqueduct's resilience against environmental and structural stresses. Additionally, the implementation of regular maintenance and repairs, as evidenced by historical records, ensured its continued functionality over the centuries.

Brief History

circa 90-95 CE

The construction on the Aqua Claudia began in 38 CE, under the orders of emperor Caligula. Most of the structure, however, was completed in 54 CE during the reign of emperor Claudius, whose name the aqueduct still bears. According to an account by Roman historian Tacitus, the Aqua Claudia, or at least part of it, was functional as early as 47 CE.

During the reign of emperor Vespasian (circa 69-79 CE) the aqueduct is known to have been repaired (sometime around 71 CE) after being nine years out of function and in disrepair.

Some ten years later the Aqua Claudia was extensively repaired again in 81 CE by Emperor Titus.

Additionally, brick stamps from 123 CE testify to some restorations during the rule of emperor Hadrian.

An inscription (CIL VI.1259) notes that Alexander Severus (reigned 222 to 235 CE) reinforced the arches constructed by emperor Nero, where they are called arcus Caelimontani, including the line of arches across the valley between the Caelian and the Palatine Hills.

During the construction of the Aurelian Walls, parts of Aqua Claudia seem to have been incorporated in to the fortifications.

In 1585 CE, a large part of the Aqua Claudia was stripped of its core materials (peperino and tufa blocks), which were reused in the construction of the new Aqua Felice commissioned by Pope Sixtus V.

Route

circa 38-96 CE

The aqueduct spanned approximately 70 kilometers (43 miles approx.), channeling water from springs near Subiaco in the Anio Valley to the city of Rome. Its main sources of water the natural springs, the Caeruleus and Curtius, were situated near the 38th milestone of the Via Sublacensis. Its route followed a combination of underground channels and elevated arches, with notable segments above ground, such as the arcades that entered the city at the Porta Maggiore. From there, it extended towards the Caelian Hill, serving key locations such as the Palatine Hill and other areas of central Rome.

At some points it was branches off to provide water to imperial estates situated along the way. One such branch was connected to the suburban villa Sette Bassi.

The aqueduct was celebrated for its dual-purpose conduit, as it also supplied water to the Anio Novus aqueduct, constructed contemporaneously. The Aqua Claudia's engineering prowess, including its capacity to transport approximately 190,000 cubic meters of water daily, highlights its critical role in maintaining the water supply for Rome's urban population, public fountains, and baths. Its course was later restored and maintained by several emperors, including Vespasian and Titus, attesting to its enduring importance within the Roman hydraulic system.

Architecture

circa 38-96 CE

The architecture of the Claudian Aqueduct comprised of underground water channels, mot likely constrcuted out of clay pipes, and above ground structures comprised of water channels raised on connected arches. The aqueduct's pillars and arches were constructed using the 'opus quadratum' technique, involving the precise placement of large, uniformly cut volcanic stone blocks (inspect) without the use of mortar, relying on the weight and fit of the stones for stability. Additionally, sections of the aqueduct were faced with 'opus reticulatum,' a method characterized by a net-like pattern of tufa stones set into a concrete core, providing both structural integrity and aesthetic appeal.

Some of the later sections, however, were constrcuted out of baked clay bricks, as seen in the Domitianic section (inspect) on the Palatine Hill.

The Romans' strategic use of durable materials such as tufa and concrete, combined with these sophisticated construction techniques, contributed significantly to the aqueduct's resilience and longevity, allowing substantial portions of the structure to endure for nearly two millennia.

Notable Surviving Sections

circa 38-52 CE

Caligulan-Claudian Section in the Parco degli Acquedotti
The original constructed section in the Parco degli Acquedotti is the longest and the best preserved stretch of the ancient Aqua Claudia. The longest continuous stretch measures approx. 1.4 kilometers starting near the Via delle Capannelle and terminating just north-west of the viale Appio Claudio. This section, however, continues for another 1.2 kilometers, running north-west, but lies mostly in ruins.

circa 38-53 CE

Campo Gerini Section
Three sections of the aqueduct remain in the "Campo Gerini" area. In this section double concrete arches with brick facing reinforcing from inside the stone arches of aqua Claudia, built in the course of repair works in Hadrianic period are also visible.

circa 38-53 CE

Porta Maggiore Section
The Porta Maggiore section of the Aqua Claudia is one of the most notable and well-preserved parts of the ancient Roman aqueduct system. The Aqua Claudia, one of Rome’s most important aqueducts, was completed in 52 CE under Emperor Claudius and extended to the Caelian Hill, carrying water from the Anio River. The section that passes through the Porta Maggiore (a monumental gate in the Aurelian Walls of Rome) is particularly significant due to its dramatic and highly visible construction, featuring a complex system of arches and channels that allowed water to pass through the heart of the city.

circa 81-96 CE

Remains of the Domitianic Extension
The Domitianic Extension of the Aqua Claudia refers to a significant expansion of the original Aqua Claudia aqueduct that was commissioned by Emperor Domitian around 81-96 CE. This extension, which expanded the aqueduct’s reach, was part of a broader effort to provide more water to the growing population of Rome and ensure the smooth functioning of the city's water supply infrastructure. The extension improved the distribution of water, bringing it to new districts of the city that had developed outside the original coverage area of the Aqua Claudia.

The Domitianic Extension of the Aqua Claudia primarily involved the construction of new sections of the aqueduct that followed the original route but were extended to cover regions such as the Caelian Hill, Esquiline, and parts of the Viminal Hill. The extension included additional arches, channels, and reservoirs to transport water to the higher and newly populated areas of Rome. In particular, the extension required adjustments in engineering to overcome uneven terrain and ensure a continuous flow of water. Roman engineers employed various techniques, including the use of elevated channels supported by monumental arches, to maintain the necessary gradient for the aqueduct. The extension continued to rely on gravity for water flow, an impressive feat of engineering that reflected the Romans' advanced understanding of hydraulics.

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