Time Magazine recently published an article about corporate sponsors buying the rights to slap temporary advertisements on historic monuments as way to raise funding for costly restorations.
As cited in Time advertisers paid 3.7 million to renovate Dodge's Palace in Venice over recent years.
I remember seeing this sort of thing in Rome and would have liked to provide a photo demonstrating firsthand evidence, but I found nothing;
I consider it to be a convenient idea, personally, so I used Adobe Photoshop to construe my own advertisement just to give you an idea of how it would work….
Huh, If only I had the 33 million dollars it will cost to rebuild the other half of the Colosseum (no they are not actually going to do that).
Faris, Stephan. "A Bridge Too Far?" Time Magazine April 9 2012: Business Pages (1-7)