The streets of Seville in southern Spain were so hot that July afternoon that it felt almost impossible to walk outdoors. As temperatures approached 42C (108F), people scrambled to find shelter in air-conditioned homes, offices and public buildings. Yet, less than two miles from the city center, a cool breeze blew under a giant white roof.

The structure is a part of CartujaQanat, an architectural experiment in cooling solutions that doesn’t rely on burning more planet-warming fossil fuels. The site, about the size of two soccer fields, includes two auditoriums, green spaces, a promenade and a shaded area with benches. But its star performer remains hidden — the qanat, a network of underground pipes and tubes inspired by Persian-era canals.

The grid of aqueducts can lower surrounding temperatures by as much as 10C using just air, water and solar power, according to Emasesa, the Seville public water company that helped to build it. The system is modeled on ancient tunnels dug to bring water to agricultural fields that were first documented in what is today Iran. The Persians realized 1,000 years ago that the running water also cooled the air in the canals, so they fashioned vertical shafts to bring that air to the surface.