When does a bus shelter become art? When it is part of the Tate Modern's new exhibition Global Cities. This is street furniture with a serious message--too bad it's just part of an art show, rather than out on the streets. For his commission, the artist Nils Norman has borrowed a bus shelter, a sign and a lamppost from London Transport and turned them into vehicles for environmental information whilst making them look like everyday advertising.

The bus shelter (pictured) has posters publicising impending environmental disasters: one explains how to make your own diesel, another proposes solutions for living in a flood zone and another tells how to combat West Nile Virus. Another extols people to "dig up your lawn and plant for victory." The roof has been adapted with a planter of drought-resistant plants such as agaves and arid plants to show how green spaces could look in the future, with climate change. In another exhibit, directional signs show a crossroads, pointing out fashionable classifications of people such as "planet of slums" and "international curators", rather than streets. The last, a huge lamppost has a cut-out of a silhouette of a man's face on it. ::Tate Modern