Someone has come up with this idea of linking buildings (and other physical locations) around the world with wikipedia articles describing them, with the help of an ISBN like machine readable tags
They have a pretty readable explanation at the site - it goes like this
1. 2. You are in Austria and you want to visit the Presidential Palace
Someone pastes the machine readable tag near the building, you read it off the page using your cell phone and voila, you get the URL on your cell phone's browser....
come to think of it, would'nt it be better just to have a tinyurl link to the wikipedia article on this piece of paper?