Vertical cities: Laurie Taylor explores the increasing segregation of cities by height. Stephen Graham, Professor of Cities & Society at Newcastle University, ponders 'class war from above'. His exploration of the built environment around the world, both above and below ground, finds that the wealthy have gone upwards; into "islands" and "archipelagos" of residential towers, hotels, private clubs, roof gardens, restaurants, swimming pools, even heliports. They enjoy fresher air, commanding vistas, safety from crime and speedy travel. Privileged Chinese citizens retreat to air conditioned citadels in the sky; wealthy Thai commuters enjoy the Skytrain, Bangkok's elevated railway for the fortunate few. Graham lays out a landscape where architecture reflects and reinforces divisions with ever greater brazenness.