A city in Southern Spain holds an ancient secret to fighting extreme heat

A few meters below the former site of Seville’s 1992 World Expo, a promising climate experiment blending ancient technology and modern science is underway. Rows of black pipes run along the ceiling and down the bare concrete walls. These, in turn, connect to bright blue and green tubes and enormous silver pumps. In a control room to the side, an array of monitors display the heat, humidity and wind speed above. “We have deployed several types of cooling systems here, each one...