Just in case you somehow managed to still have any kronur in your wallet.

And even if you don't, they take credit cards!

(More seriously, Iceland still has capital controls, so you do have to jump through a slight bureaucratic hoop to change Icelandic money into anything else. I had to show my ferry ticket to the Faroes--which was photocopied and put on file somewhere--before the bank could legally change Icelandic krónur into Danish kroner.)