The Musée Cognacq-Jay is Paris' best (and admission-free) private gallery of 18th century painting

Back in the early 1900s, the couple who founded the grand La Samartaine department store—Ernest Cognac and Marie-Louise Jay—amassed a magnificent collection of 18th-century art, which they generously left to the city.

Now it's housed in one of the chichi mansions in the Marais district, preserved in all its 18th-century glory.

Fair warning: this is only for folks who don't get mental cavities from playful, pastel paintings and fussy objets d'art by the likes of Watteau, Fragonard, Boudin, and Chardin.

Then again, even if that stuff bores you to tears, since it's free, why not pop in at least to get a quick sense of the prevailing tastes and lifestyles of the rich and French and famous in the 1700s? (No wonder the peasants revolted.)