Ancient Records

In ancient Egypt, when pharaohs wanted to record something for eternity and have it be known not only to mortals, but more importantly, to the gods, they wrote in stone.
from Nova – Riddle Of The Sphinx

And thousands of years later these stones, or stelas, remain to give us an historical record and glimpse into ancient civilizations.

When we become an ancient civilization to those who live thousands of years from now, what record for eternity are we leaving that will still exist (and function) for them to discover and decipher?