Potatoes growing out of the ceiling in a tunnel. It's an ad by Lays: 'our potatoes are grown closer than you may think.' Could be an interesting street art concept, hanging growing stuff in subway tunnels etc.
Saw his clever work all over Firenze. If it makes people pay more attention to street signs, than I say, why not give him a public works grant! Clet-Abraham_Street-art_stickers-on-traffic-signs_multi_collabcubed