MODERN WORLD

World’s Busiest Cities, 8pm, BBC2

EPISODE two finds Dan Snow, Anita Rani and Ade Adepitan going behind the scenes of the dizzyingly chaotic megalopolis of Mexico City, home to more than 21 million people. Perched in the midst of a deadly earthquake zone, how does such a vast, rambling urban sprawl manage to survive, let alone keep growing?