Since 1869, the Casino de Monte-Carlo has generated so much money for the Principality of Monaco that the ruling Grimaldis stopped taxation. This action made Monte Carlo a tax haven and playground for the wealthy. Today, the residents are 80% to 90% foreigners. Monaco has become one of the world’s most expensive places to live. This is probably okay because the country also has the most millionaires per capita. Ironically, no local residents are allowed inside the casino. You must present a foreign passport to gain entry.