Toynbee tiles (also called Toynbee plaques) are messages of mysterious origin found embedded in asphalt in several major cities in the United States, and in three South American capitals as well. As of 2006, there are approximately 130 tiles, which are generally about the size of an American license plate but are sometimes considerably larger. They all contain some variation on the following inscription:
TOyNBEE IDEA
IN KUbricK's 2001
RESURRECT DEAD
ON PLANET JUPiTER.
Right up your alley. I'll assume you have no involvement, since I don't think you've been traveling to South America.