This could work in Birmingham, we have quite a lot of dirty underpasses. It could also work well in Barcelona which is similarly filthy….though, to be pedantic, Barcelona is more smelly than filthy. If you were a very clever conceptual artist, particularly the type that likes to do something incredibly technically difficult for a barely perceptible result, you could perhaps conceive of a way to etch clean air designs into the atmosphere of particularly smelly barrios. Stringy-haired Catalan youth would have to pass up and down the narrow streets, many times, sniffing constantly, before the true complexity of the design would become apparent.

If I was a socially aware, edgy, clandestine, reverse-graffiti-artist operating in Birmingham I would collect all the litter that is stuck in bushes around the bottom of blocks of flats. Then I would re-attach it to the bushes, but in such a way that it spelled out the phone-number of the council’s waste collection service. This would be a scathing attack on the council’s apparent neglect of run-down areas. But I suspect that litter isn’t very cool – it’s probably a bit suburban and small minded to worry about it – I’d probably get kicked out of the reverse-graffiti-artist gang tree hut (which is where I like to imagine they hang out – I really hope they do).