Collateral is in order. I would suggest the Elgin Marbles. They are ancient perfection and of immense, imeasurable valuec
I'd bet they'd give the Greeks an island of comparable size somewhere in the Gulf of Bothnia ~ any time!
Perhaps the Parthenon instead. Of the Greeks default the Finns pack it up and move it to Helsinki.
For that matter, much of the ancient marble architecture and statuary that remains in Greece is reportedly deteriorated horribly from the effects of local air pollution, poor maintenance, and indifferent stewardship.
*Apparently, Greeks don't like to hear these national treasures referred to as “Elgin” marbles and prefer the term “Parthenon Marbles”.