Like any asset, they can be exchanged to anyone who will purchase them.
Banks do not deal in precious metals.
You would most likely sell them back to a precious metals broker and there are lots of those out there. Individuals, pawn shops, etc are also an option if you can get a price you like.
Just an FYI...Gold has been at all time highs for a while now. General investing principles say to buy low, sell high. Where will Gold go in a few years? We don't know. Most experts in the field are not considering it a good time to get into the Gold market.
I am not a market analyst, these are not opinions of my own and this (plus a truckload more) of information on precious metals is available from any popular precious metals site.
For prices, check out:
For buying, check out: