When I was about 11 years old me and my life-long best friend, Jaime, thought it would be a fantastic idea to make a time capsule, and fill it with all the little sentimental objects from out childhood (things like baby bracelets, photographs, little toys, even my old blankie!) and we also wrote letters to eachother, saying how we loved being best friends, and we'd always stay "friends forever" (It was probably the nicest letter I've ever written anyone).
We wrapped it up and buried it one afternoon in my backyard, next to this big tree that was there at the time.
I remember we made a pact, that in 10 years time when we were 21 we would come back and unearth it, and remember the days of our childhood...
But time went on, and soon we forgot about the time capsule...
About 3 years ago we got an extention built onto the back of our house, and alas, we didn't remember the time capsule until maybe a year later.
Our house now lies over our capsule, (I'm pretty sure it's underneath our new bathroom) and we can't get to it.
At least it's safe there, I guess...

So yeah, this was a learning experience because I learnt you shouldn't bury sentimental objects (to start with) or bury them where a house might lay in the future.