Aqueduct of Segovia: Spain's Great Roman Aqueduct Bridge

The Aqueduct of Segovia is a Roman aqueduct in central Spain whose great granite arcade still strides across the centre of the city. Built in the late first or early second century AD, it carried water from the mountains of the Sierra de Guadarrama to the Roman town of Segovia. Its arches, fitted together without any mortar, are among the best-preserved examples of Roman engineering anywhere and have become the emblem of the city.

Background: water for a Roman town

Segovia lay in the Roman province of Hispania Tarraconensis, on a rocky ridge between two rivers in the meseta of central Spain. The Romans built aqueducts to supply towns with a steady flow of clean water for public fountains, baths and wealthy households, and to show off the benefits of Roman rule (see Aqueducts of Ancient Rome).

Water at Segovia came from the Río Frío, a stream in the Sierra de Guadarrama. To reach the town on its ridge, the channel had to cross a dip in the land where the modern Plaza del Azoguejo lies. There the engineers built the arcade that has made Segovia famous.

Segovia in Roman times

Before the Romans, the area was home to Celtiberian peoples, and the hilltop site was probably already settled. Segovia came under Roman control during the long conquest of the Iberian Peninsula, completed under Augustus in 19 BC. Under the empire it developed into a Roman town, a municipium, though much less is known about its streets and buildings than about its famous aqueduct.

The aqueduct was a major public investment for a town of modest size. It suggests that Segovia had wealthy citizens or strong imperial support, and that its leaders wanted the comforts associated with Roman urban life, such as public baths and fountains.

When was it built?

The aqueduct’s date has long been debated. There is no surviving ancient text describing its construction. A bronze inscription once fixed to the upper part of the arcade has been lost, and only the holes for its letters remain.

Attempts to reconstruct the text from those holes, notably by the German epigrapher Géza Alföldy, have been used to argue for a date around the end of the first century AD, but the reading is not certain. Other scholars, citing archaeological evidence from around the foundations, prefer the early second century, under Trajan or Hadrian. Most modern accounts therefore date the aqueduct broadly to the late first or early second century AD.

How the aqueduct worked

The aqueduct was about 15–17 kilometres long from its source to the town, depending on how the route is measured. For most of that distance the water ran in a covered channel at or below ground level, following a gentle slope. Like all Roman aqueducts, it relied entirely on gravity.

Near the city, the water passed through a settling tank, now known as El Caserón, where sand and grit could sink before the flow continued. A second tank, the Casa de Aguas, did the same job further on. The channel then reached the arcade, crossing the valley on top of the arches in a narrow U-shaped duct, before entering the upper town and running towards the area of the later Alcázar.

The arches

The visible bridge section runs for roughly 800 metres. It has around 167 arches, counted differently by different authors, and rises to about 28 metres at its highest point in the Plaza del Azoguejo. In the deepest part of the valley there are two tiers of arches, one above the other; elsewhere a single tier suffices.

The structure uses an estimated 20,000–24,000 blocks of local granite, roughly squared and laid without mortar or cement. Their stability depends on the precise balance of forces in the arches and pillars. Building the arches required temporary wooden frameworks, called centring, to support each arch until its keystone was set. Workers would then move the timber to the next span. Stone was quarried nearby in the Guadarrama foothills, which reduced transport costs.

Small holes visible on many stones were probably used to grip them with lifting tongs or clamps while they were hoisted into place.

Above the central arches, a block of masonry once carried the lost bronze inscription. Two niches in it now hold Christian images placed there in later centuries.

Damage and rebuilding

The aqueduct survived the end of Roman rule and remained in use. In 1072, during an attack on Segovia by forces of the Muslim taifa kingdom of Toledo, about 36 arches were destroyed.

In the late fifteenth century, under the Catholic Monarchs Isabella I of Castile and Ferdinand II of Aragon, the damaged section was rebuilt. The work, begun in 1484, was overseen by Juan de Escobedo, a monk of the nearby monastery of El Parral. The rebuilders closely copied the Roman arches, although careful observers can distinguish the rebuilt stretch from the original Roman work.

The aqueduct continued to carry water to Segovia into modern times. In the twentieth century, traffic passing beneath the arches and air pollution began to damage the granite. Restoration work was carried out from the 1990s onwards, and the road under the arches was closed to motor vehicles.

Its survival is remarkable. Many Roman aqueducts were abandoned when cities shrank after the fall of the western empire, and their stones were reused for other buildings. At Segovia the arcade stayed useful, and the town kept maintaining it for centuries, which helps explain why so much of the original Roman structure still stands today.

Legend and symbol

Local tradition calls the aqueduct the “Devil’s Bridge”. According to a popular legend, a girl who carried water up the hill each day promised her soul to the Devil if he could bring water to her door before the cock crowed. He worked all night, but the cock crowed just before he placed the last stone, so she kept her soul. Legend adds that holes in the stones are the Devil’s fingerprints.

The aqueduct appears on the coat of arms of Segovia, and in 1985 the Old Town of Segovia and its Aqueduct were inscribed on the UNESCO World Heritage List. It is often compared with the Pont du Gard in southern France as one of the finest surviving Roman aqueduct bridges.

By the numbers

Timeline

• Late 1st – early 2nd century AD: the aqueduct is built for the Roman town of Segovia.
• 5th century AD: Roman rule in Hispania ends; the aqueduct remains standing.
• 1072: about 36 arches are destroyed during a raid from Toledo.
• 1484: rebuilding begins under the Catholic Monarchs, led by Juan de Escobedo.
• 1985: the Old Town of Segovia and its Aqueduct become a UNESCO World Heritage Site.
• 1990s: major restoration work and traffic restrictions begin.

Why it matters

The Aqueduct of Segovia shows how Roman engineers combined simple materials with precise geometry to create structures that have lasted for almost two thousand years. It brought Roman ideas of public water supply to the interior of Spain and still dominates the city that grew up around it, a rare ancient monument that remains part of everyday urban life.