At the main Paris international airport there is a prison, and this is where the French put people who arrive without a valid Visa, passport or money to buy a return plane ticket. Those without a passport/visa are given the choice of buying a return plane ticket or going to the airport prison.
I only bring this up because there are a lot of countries (like Hungary) who have drawn a line in the sand to stop illegal immigration. The world does not scream and yell about how cruel and heartless these countries are.
Yep, most people who have never traveled outside the country would NOT be aware of this.