Monaco, the richest 0.76 square miles on the Mediterranean, is not exactly the Frugal Traveler’s kingdom. This independent principality is synonymous with money — big, untaxed money — and ways of spending it: fast cars, luxury goods, gourmet meals and high-stakes gambling. That was apparent even on the five-hour train ride from Montpellier (41.60 euros, or about $67 at $1.61 to the euro; www.voyages-sncf.com) along thegorgeous French Riviera. Instead of backpacks and sandals, my well-tanned fellow passengers were armed with Louis Vuitton handbags and Gucci sunglasses.