I know that money exchanges work on the principle of selling foreign currency for more money than they are buying it. In an ideal market, there would be an equilibrium in the money being imported and exported (and there probably is one, actually), and the price would reflect the current supply and demand.
However, then the holiday season happens and people from the less attractive countries start visiting more attractive countries, creating an imbalance between cash exported and cash imported. Since it is still possible to exchange money during the holiday season for a reasonable price, I assume that large sums of money are somehow transferred back from the holiday countries.
I'm pretty sure it's not the handful of tourists who travel to, say, Latvia from Croatia.
How is physical money transferred back from these holiday destinations?