Billboards are good for more than advertising.
Architect Didier Faustino made Double Happiness out of an old billboard in New York City:
Double Happiness responds to the society of materialism where individual desires seem to be prevailing over all. This nomad piece of urban furniture allows the reactivation of different public spaces and enables inhabitants to reappropriate fragments of their city…
They will both escape and dominate public space through a game of equilibrium and desequilibrium. By playing this “risky” game, and testing their own limits, two persons can experience together a new perception of space and recover an awareness of the physical world.