Damn Interesting had a well-written look at the mysterious Toynbee plaques/tiles,
In 1992, a chap in Philadelphia by the name of Bill O’Neill starting noticing strange tiles randomly embedded in local roads. They were generally about the size of a license plate, and each had some variation of the same strange message: “TOYNBEE IDEA IN KUbricK’s 2001 RESURRECT DEAD ON PLANET JUPiTER.” They varied a bit in color and arrangement, but they were all made of an unidentifiable hard substance, and many had footnotes as strange as the message itself, such as “Murder every journalist, I beg you,” and “Submit. Obey.” Some were accompanied by lengthy, paranoid diatribes about the newsmedia, jews, and the mafia.
So Bill started asking around about these tiles, but nobody knew anything about their origin or meaning. So, he created a website devoted to the mysterious tiles, and in doing so learned that it is not just a local phenomenon. Similar tiles have appeared in many US cities, including Washington DC, Pittsburgh, New York City, Baltimore, Boston, and many more. Some have even shown up in South America; in Brazil, Argentina, and Chile. To date, about 130 tiles have been discovered. Somehow, someone is managing to embed these tiles into public roadsâ€“ some of which are busy 24/7â€“ without being spotted.
Toynebee.Net has a list of locations where the tiles have been spotted in the United States, and the handful of tiles that have been spotted in South America.
The Toynbee referred to is believed to refer to historian Alfred Toynbee, who died in 1975.
Almost as weird as those Andre the Giant Has a Posse stickers.