I've heard that international airports have tax duty free zones which contain artwork. The artwork is held there, it never moves, but it is sold from person to person without tax. 

I wonder if Bitcoin could be held in those vaults 

 My mind is a tax-free zone.  

 yep, but bigger facilities like that are not in airports.  they are allowed by that govt, and so don't need to be.
it's a fascinating rabbit hole.