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Dec 18th 2019

The Aqueduct of Segovia: Ancient Engineering’s High Water Mark

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Rome rises again — literally. This trip into the engineering wonders of our world takes us almost 30 meters (nearly 100 feet) off the ground to analyze the Aqueduct of Segovia, one of the best-preserved Roman waterways. Nearly two millennia old, the structure may not match the pyramids for sheer longevity but remains an enduring symbol of Rome’s commitment to building functional and almost frighteningly over-engineered edifices of efficiency.

Let’s dive in and discover the why, what, where and how of this ancient Roman engineering feat.

Water, Water Everywhere

Roman aqueducts were designed to carry water from local springs or rivers to cities or towns. As noted by Interesting Engineering, during the early Roman imperial era, these aqueducts delivered water to more than a million people across the empire.

The Aqueduct of Segovia is a classic example of Roman water transport architecture, with parts of the original system still in use today. Located in Segovia, Spain, this system starts at the Frio River, approximately 15 kilometers (almost 10 miles) from the city itself, according to the World Monuments Fund. Partially buried underground and using the natural landscape to direct water flow, the aqueduct eventually reaches a 30-meter (nearly 100 feet) deep valley; to cross the span, Roman engineers built what is commonly referred to as the Aqueduct of Segovia — a two-tiered set of arches and channels with foundations 6 meters (about 20 feet) deep.

While the exact time of construction is unknown — some sources suggest 50 A.D., others push the data forward to 100 or 120 A.D. — any variance pales in comparison to overall longevity; few modern structures make it past the 100-year mark, let alone two millennia.

Duct and Cover

Likely built under the rule of either Emperor Domitian, Nerva or Trajan, the Segovia aqueduct was a critical infrastructure project. While the town itself was small and isolated, Ancient Origins notes that Segovia was located on the main road between two larger Roman settlements, making it an important stop for goods and travelers alike.

According to the Encyclopedia Britannica, the aqueduct bridge was constructed using more than 24,000 granite blocks — also called ashlars — held together without mortar. Its highest point is almost 30 meters (nearly 100 feet) above ground, with a six meter (about 20 feet) deep foundation to support the nearly 20,000-ton span of arches. While most Roman aqueducts relied on a single tier of arches to reach the necessary height, the sharp drop-off into the valley just before Segovia itself required a second level to ensure water flow. The sheer scope of the bridge project helped cement its place in history and explains why many descriptions of the aqueduct focus on the span itself, which represents just 5% of the project’s complete length.

Focusing on the bridge in isolation also ignores essential Roman innovation: desanding basins, known as “desarenadors,” at multiple points along the aqueduct route. By slowing the flow of water through these basins, Roman engineers were able to leverage the process of decantation and remove the bulk of river sand from their water supply, improving both quality and safety. Building the aqueduct system likely took between two and five years, from initial planning stages that included water quality testing, slope analysis and evaluation of the physical condition of locals who regularly drank from the source. Slaves were the typical source of labor, and would have been required to both move heavy blocks by hand and dig massive trenches to support channels and foundations.

The original bridge work contained three niches with bronze plaques that listed builder names and construction dates. One included an image of Hercules — supposed founder of the city — but all have since been lost.

Liquid Longevity

Now a World Heritage Site, the Aqueduct of Segovia is both a tourist attraction and testament to Roman ingenuity. But the waterway hasn’t always fared so well — while later projects used more resilient Roman cement, the granite blocks of Segovia began to erode over time. This was especially evident in the desanding chambers, which required regular cleanings to remove sand buildup and replace damaged stonework. After the fall of the Roman Empire, many fell into disrepair.

In 1072 A.D., an invasion by Yahya ibn Ismail Al-Mamun destroyed approximately 36 arches; some of the dislodged stones were then used to rebuild the castle of King Alfonso VI. In the late 15th century the damaged aqueduct sections were rebuilt, with further preservation efforts in the 16th, 17th and 18th centuries. Between 1803 and 1806, all buildings adjacent to the bridge were demolished to make repairs easier and increase structural integrity.

While the Aqueduct of Segovia doesn’t hold the title of Rome’s biggest aqua architecture project — Pont du Gard gets the nod for highest bridge and Constantinople gets the most sophisticated system award — the waterway is nonetheless a feat of ancient Roman engineering that represents a high water mark in the empire’s ability to streamline, strengthen and support critical infrastructure.

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