Bury it and mark it
Burying it deep is a sound idea, but the site needs to be marked well so that people in 10,000 years know not to go fossicking around underground. That's tricky - a nice painted skull and crossbones is likely to have faded.
How about a nice big ring of giant granite stones raised up on end with more stones across the top, and a massive slab in the centre marking the entrance? Should be good for a few millenia...