Beneath a public square in Athens lies an engineering marvel that has been dormant for centuries. A part of it passes under a cafe called Dexameni, yet most patrons are unaware of the history just feet below them, but they will soon start using it.

“Ninety-five percent of customers don’t know the aqueduct exists,” Nektarios Nikolopoulos, the cafe’s owner, told the New York Times last year. “They know Dexameni for the cafe, not its history.”

The Greek capital is grappling with a massive heatwave, with temperatures hovering over 40 degrees Celsius (104 F) for several days. This is deepening an already severe water crisis that has brought the city’s water reserves to the limit. In desperation, officials are turning to this hidden relic: a 15-mile-long aqueduct commissioned by the Roman Emperor Hadrian nearly two millennia ago. In the coming weeks, water will once again flow through its ancient channels to serve the city above.

A New Purpose for an Old System

The crisis has been building for years. Last September, the Mornos Dam, about 124 miles west of Athens, dried up so completely that it revealed the ruins of a village submerged since the 1970s.

The city’s two main reservoirs, Lakes Mornos and Evinos, have shrunk by about 40% of their usual surface area. Last year, they were at 80%, and in 2022 they were near full capacity. Faced with this grim situation, the Athens Water Supply and Sewerage Company started looking outside the box for solutions. They ended up finding an idea right beneath their feet.

The Hadrianic Aqueduct was a masterpiece of its time. Commissioned in 125 AD and completed 15 years later, it was not merely a channel for transporting water but an ingenious system for collecting it. The aqueduct was the main water supply for the region for centuries, operating without any major changes until the Ottoman occupation in the 15th century.

The aqueduct operates through a gentle, gravity-fed slope. But its true genius lies in its design as a collector. “It’s an underground channel,” explained Giorgos Sachinis, the director of strategy and innovation at the Athens Water Supply and Sewerage Company, in a recent interview with NPR. “The way it operates, it infiltrates water from the groundwater table into this channel.” The running aqueduct extracts water from underground aquifers as well as from above-surface water streams.

This intricate network was originally built, likely by enslaved workers, by digging hundreds of vertical shafts, or wells, and then tunneling horizontally between them to meet in the middle. Of the 456 original wells, around 390 are known to survive today. The modern plan, however, comes with a key distinction: the water from the aqueduct will not be for drinking.

“The whole purpose is to get this water out of Hadrian’s Aqueduct before it reaches the ending reservoir because it will not have the standards of potable water. So, we need to find the nonpotable uses like urban irrigation, washing of the streets, fire protection, industrial uses — this sort of thing.”

A Blueprint For Sustainability

Athens is far from the only city grappling with severe drought. As climate change becomes more and more severe, water availability is becoming a crisis afflicting numerous regions globally. Similarly, Athens is not unique in possessing ancient water infrastructure that offers potential solutions. Many cities across the former Roman Empire, such as Rome itself, Nîmes in France, and Segovia in Spain, are home to monumental aqueducts. Some of these aqueducts are already in use, including the ancient qanats (underground aqueduct tunnels) of Persia and the pre-Incan puquios in Peru.

Now, this past utility is providing a blueprint for future sustainability.

Instead of relying on carbon-intensive new construction, this approach repurposes existing assets. It’s basically a circular economy on a centuries-old scale. Because these ancient systems are often gravity-fed, they require minimal energy compared to modern pumping stations, significantly reducing their operational footprint.

Engineers are tapping into 20 of the ancient wells to serve as access points for new, local water networks. For an initial trial, a 2.5-mile pipeline has been built to connect the aqueduct’s central reservoir, which sits beneath Dexameni Square, with suburban neighborhoods. The pipeline will first supply non-potable water to civic buildings and, eventually, to about 80 homes. The first of these local networks is expected to begin operating by the end of July or in early August, with the full project slated for completion by 2029 at the latest.

While this is an exciting project for Athens, and offers hope for cities in similar situations, it’s a sobering reminder that ‘business as usual’ just doesn’t cut it in the current climate. This project is a clever adaptation born from desperation, and it’s only useful as a temporary stop to the problem. Ultimately, it cannot single-handedly replenish Athens’ vast, shrinking reservoirs or reverse years of prolonged drought. To do that we need to fundamentally reshape our modern world’s relationship with water itself.