Archaeologists working beneath the streets of Zaragoza in Spain have uncovered the remains of a 2,000-year-old Roman structure believed to be part of a bridge with aqueduct functions. The discovery is offering new insight into how the ancient city of Caesaraugusta was designed and how it managed its water supply.
The find was made during urban renewal works at San Miguel Square and along the historic Coso Avenue. As infrastructure upgrades progressed, archaeologists monitored underground layers and identified a large Roman arch about four meters (13 feet) below the present-day street level.
A rare dual-purpose structure
The arch was built using opus caementicium, a durable Roman hydraulic concrete commonly used in major infrastructure projects. Researchers say the structure likely served two purposes. It may have supported movement across a low-lying area while also carrying water into the city.
Such combined bridge-aqueduct systems are rare in Roman engineering. Experts say the design reflects efficient planning, allowing engineers to solve multiple challenges with a single structure.
The remains were found near the intersection of Coso and Espartero Street, an area that in Roman times lay over a shallow valley. Archaeologists believe the structure once crossed this terrain, helping manage both transport and water flow within the city.
Early construction linked to the Augustus era
The materials and construction style suggest the structure dates to the early years of Caesaraugusta. The Roman colony was founded during the reign of Emperor Augustus in the late first century BC. Researchers say the discovery shows that advanced infrastructure planning was part of the city from its earliest phase.
A 2,000-year-old Roman bridge has been uncovered beneath the streets of Zaragoza, Spain.
Archaeologists say the structure may have also carried water into the ancient city—making it a rare bridge-aqueduct system. pic.twitter.com/zGlgbrBVxt
— Tom Marvolo Riddle (@tom_riddle2025) March 18, 2026
José Juan Domingo, head of Zaragoza’s Municipal Archaeology Service, said the find is highly significant. He explained that it is the first structure of this type identified in Zaragoza and provides valuable information about how the Roman city organized its water supply and urban layout.
New clues about the city’s size and layout
The discovery is also changing how researchers understand the extent of ancient Caesaraugusta. For years, scholars debated whether the area between Coso Avenue and the Huerva River was a later suburban expansion.
New evidence suggests the zone was part of the original city. This indicates that Caesaraugusta may have been larger and more integrated than previously believed.
Preservation and ongoing research
After excavation, the archaeological team carried out full documentation, including photography, detailed drawings, and 3D scanning. Authorities chose to preserve the structure in its original location beneath the pavement. The remains were carefully reburied so that urban work could continue without damage.
Researchers have opened an additional test excavation nearby to determine whether more sections of the structure survive underground. If further arches or channels are found, they may be able to reconstruct the full size and function of the structure.
Artifacts and historical challenges
Excavations also produced pottery fragments and other artifacts from different historical periods. These items have been sent to municipal laboratories for analysis and cataloging.
Archaeologists note that many remains in Zaragoza are fragmented. For centuries, construction took place without archaeological supervision, which damaged earlier layers. Systematic monitoring of urban works only began in the 1980s.
A hidden Roman city beneath modern streets
Despite these challenges, each discovery adds to the understanding of Zaragoza’s past. Founded as Colonia Caesar Augusta, the city was one of the most important Roman centers in the Ebro Valley and the only one named after Emperor Augustus.
Much of its ancient infrastructure remains buried beneath the modern city. The newly discovered bridge structure highlights how parts of Roman Zaragoza still lie hidden underground, waiting to be revealed as development continues.
