Seville resurrects 3,000-year-old solution to cool its summers

World Half Full
Feb 20
4 min read

COMMUNITY/ENVIRONMENT

The Spanish city of Seville is blending ancient technology and modern science in an attempt to cool its oppressive summers.

In 2020, authorities began installing cooling systems in two public spaces in the Isla de La Cartuja neighbourhood of Seville, one of Europe’s hottest cities. Every day about 30,000 people come to work and study in this northwestern district of the city, which is mostly non-residential and home to university campuses, museums, and businesses.

That cooling system, which is called CartujaQanat, is a network of underground aqueducts called “qanats”. These have been constructed in a newly-built 750-square metre site known as the Agora, which can hold about 400 people, as well as in a renovated amphitheatre from the 1990s that has a capacity for about 200 people. Most of its funding comes from the European Union.

The system, created millennia ago but updated for the 21st century, works by cooling water underground at night. To speed up the cooling, some of that water is also sent to the roof via solar-powered pumps and sprayed out of nozzles in a thin layer through a method known as a “falling film”, before draining back down underground.

By day, as outdoor temperatures peak, the cool water is sent above ground into the ceiling to counteract the heat. Water is also funnelled into subterranean pipes that cool air (up to 36,000 square metres an hour), which is then released via ducts in the public spaces. Outside, mist is sprayed in order to lower temperatures through evaporation.

“We have half re-invented the qanats, taking from their engineering ingenuity,” says project head, Lucas Perea Gil, whose team began operating the cooling system in 2022, running seasonally from March to October.

The original qanats, according to Nilou Vakil, an associate professor of architecture at the University of Kansas, date back 3,000 years to ancient Persia (modern-day Iran). The same system has been used across the Islamic world, from Baluchistan to Jordan. Historically, she says, they were used in arid areas to transport water from underground sources to irrigate crops and feed animals, but also to cool homes.

“That’s how they were able to create civilisation in places you couldn’t have humans living in before,” explains Vakil, who has researched the history of the qanats. “They allowed people to live with heat before the arrival of electricity.”

The qanats also represents something of a revival of past local practices. Similar water management technologies were deployed by the Moors across Andalusia, including at Granada’s Alhambra, several hundred years ago.

Seville is Spain’s fourth largest city and home to 1.5 million people. Last year it recorded 30 days above 40°C compared with an average of just under 13 days a year over the previous decade. The city gets so hot it’s earned the unenviable nickname of the “Frying Pan of Spain”. Seville is the first city in the world t o name and categorise heatwaves. The Carlos III Health Institute estimated about 1,180 people died during a heatwave in Spain between May and July last year. Researchers have calculated that more than 11,000 people died due to extreme heat in Spain during the summer of 2022.

Seville has historically adapted to heat through its narrow streets and shaded courtyards. Now, along with the updated qanats, the city is deploying heat-reflective paint, wind and sun blockers, and vegetation on interior walls to help reduce the heat.

Research by the University of Seville has found CartujaQanat has helped lower indoor temperatures by as much as 12°C compared to the outdoors during the summer of 2025.

The other positive with this project is that it requires zero energy. During the summer of 2025, CartujaQanat’s 380-square-metre rooftop solar panels produced 55,000 kWh, while running the machinery such as pumps consumed 42,000 kWh.

“It demonstrates that ancient tech can hold a very important point in our current environment,” says Vakil. “Cooling is one of the biggest issues that we are going to face in the future. Seville’s project serves as a scalable prototype.

Already important lessons have been learned for future iterations, such as that only three of the nine water pumps they bought were needed. “We thought we needed more,” says Gil. “But we didn’t. We learned from that. So, in the future, this model can be cheaper.”

CartujaQanat’s success has led to delegations from California, Germany and Dubai, among others, to visit the site to draw inspiration and take notes. But it won’t work in all cities. As Vakil points out, the qanat system is unlikely to be effective in humid climates since it relies on evaporation.

Another plus: the project is also helping revitalise the Isla de la Cartuja neighbourhood, which despite its proximity to the city centre, is a largely underused area. Local workers come to relax in the Agora during lunch breaks, teenagers use it to skateboard, and there are regular classes for all kinds of dance: hip hop, flamenco, swing and tango.

According to Gil, reclaiming the space for socialising is a significant motivation, particularly as extreme heat can force people to take shelter in their homes. It also shows how cities can redevelop large and unused public spaces. “We wanted to create a comfortable space that people don’t have to pay for,” he says.

Charo Sollero, who began running tango classes for groups of up to 60 people last year, is one such beneficiary. “It’s an open space that’s not too hot, it’s perfect for us,” she says. “We get together to eat and drink and then dance for hours and hours.”

While the floor is not made of wood, the material traditionally used for tango dancing, the space is a much cooler option than the hotel they previously met up in.

And there’s more to come. Next year, Seville will roll out the system to other locations, including a bus stop, a square and a school in the city’s Macarena neighbourhood. “We believe they can help us live with the heat that is coming,” says Gil.

TOP Seville, Spain

MIDDLE The design of the CartujaQanat

Rendering courtesy University of Seville

BOTTOM VSwing dancers in the Cartuja Qanat 3

PHOTO Sevilla Swing Dance