Edwardian posters invited Londoners to go down to the Bakerloo line on a hot day and cool off. You would not try that now. A century of trains running through deep, unventilated tunnels has raised the temperature of the earth around them, and nobody is sure how to retrofit a fix. Jonn Elledge on the problems cities build for themselves without noticing.
Full episode: https://youtu.be/PmixA8NmojQ