Wired news has recently posted an interesting story about how to warn future generations (or aliens?) of the 1,000s of tons of 'monstrously dangerous' left-overs from the nuclear weapons program. they discuss the use of pictographic danger signs which will be tested on people from far-flung cultures to discover those that are universally legible, even after a period of 10,000 years.
next to the fact that living beings that are able to break through meters of concrete probably also would posses some sort of nuclear radiation sensing equipment, this seems an interesting problem: how would one best 'visualize' danger in a timeless manner?
[wired.com (story) & wired.com (pictures)]