It's clear the safest place to hide something is in a place:
A ) with no link to you
B ) with essentially no chance of being disturbed
Thus, to fufill those requirements you choose to bury the goods as deep underground as possible, in an uninhabited rural area where no one will bother it. Only you know the location of the goods. Done properly, there is no meaningful chance of it being discovered by happenstance, and essentially no chance of discovering it intentionally either unless you yourself spill the beans. Even a person or government with the most vicious vendetta against you will not be able to afford to dig up the whole world, or even a whole county, looking for your treasure. At that point you become the weakest, the one, and the only link to the hiding place.
[I suppose with GPS and encryption and such you could devise a way that even you would not know where the hiding spot was. Perhaps you bury it, but wander in the wilderness quite a bit and don't pay attention to your surroundings. You thus only have a very vague idea of where it is. You do make a note of the immeditate surroundings, i.e. "it's south of a rock" because of GPS's circle of error problem. But there is no way you'd ever be able to find the spot again. You carry a GPS device of some sort however, which records and stores the coordinates in a file which can only be unlocked with two passwords. One password, you know; the other, a partner knows. Now even if you are captured and tortured by some enemy, you are literally incapable of leading them to the treasure. The partner likewise. You would both have to be compromised simultaneously to be able to give up the secret. One could even encode a self-destruct password in the program/file storing the coordinate, so that if you'd rather have the treasure lost forever than fall into the hands of the feds, you could tell them "OK, OK, I'll put in the password" and then make the choice to wipe it out forever. All the above is just a silly intellectual excercise and probably not useful for real life, but I thought of it so thought I'd share. Here, I'll put it in brackets.]
However, burying assets in the wilderness tends towards inconvenience. It is impossible to make easy electronic withdrawals. Your employer will be unable to use ACH to automatically deposit your salary into this account. It would be problematic to pay your bills with such a stash. You cannot carress and admire your lovely bullion. So although it's safe, it's inconvenient. If you anticipate yourself ever having to flee quickly and not get the chance to dig up your treasure, nor to ever return to the area, this may not be the safest method for your particular situation either, despite what I said at first. So, we should consider how to hide things near to yourself as well.
I think of it like an easter egg hunt. Just imagine everywhere you would look, and try to one-up yourself. Hide it somewhere no one would ever, ever look. For instance, would anyone think to tear open all those macoroni and cheese boxes looking for cash or gold? I think not. Even better, following that train of thought, you could carefully remove the label from a can of food, cut it in half, re-solder it, and put back the label. Or figure some even better way to open and perfectly re-seal a can. Who is going to open every single one of your canned goods (this is where the food storage thing can help you even more) to hunt for a stash; a stash that you've never even told anyone about and that no one has any reason to believe you have?
And so yes, to re-iterate that last sentence, one of the most important layers of protection and hiddenness to give your stash is the layer of secrecy. No one will spend a lot of time looking for something if they have no clue it exists.