Cities are tackling rising heat – but they have to avoid a dangerous trap

Heat has become a major health threat to cities, with record numbers of deaths being recorded in urban areas around the world. Composite: Guardian Design/AP

Beneath the streets of Seville – the city nicknamed “El Sartén”, the frying pan of Europe, where summer temperatures regularly top 40C – a €5m (about £4m ) cooling strategy is taking the city back in time.

The millennium-old Persian technique of “qanat” features underground channels filled with water and shafts that bring the cooler underground air to the surface. Seville is doing the same, adapting a 1992 experimental qanat to use renewable power and – in a new twist – pumping the water to the tops of buildings, where it will trickle down inside the walls to cool them. Even the benches will be chilled.