There's no way to be a Scrooge about Christmas in Paris—after all, festivities last from mid-November to mid-January. But since New Year's Eve (known here as la Saint-Sylvestre) is not family only, it's especially nice for the city's visitors. Marking the run-up to each year's end is a public sport, one that seems to put the whole city in a better mood. If you're actually in Paris, take advantage of this! Just closing all encounters with a bonne année or bonnes fêtes à vous will provide a shot of instant gratification. Not to mention the feasts and events, the light shows installed in 125 streets, the special ice sculptures on the Champs Elysées—or the magical circus machine at...