Café de Flore is the most famous of the Saint-Germain literary cafes, a place where Sartre, de Beauvoir, Camus, and Picasso were regulars during the postwar years of existentialism and intellectual ferment. The Art Deco interior — red banquettes, mirrored walls, dark wood — has barely changed since the 1950s.
The coffee is excellent; the prices are steep but you're paying for the address. Come mid-morning for the best atmosphere: the terrace fills with a mix of intellectuals, tourists who've done their homework, and local St-Germain residents reading Le Monde. Avoid peak tourist hours if you want to linger.
Les Deux Magots, directly across the street, is equally famous (and equally pricey). Harry's Bar and Brasserie Lipp are both within a short walk and complete the classic Saint-Germain cafe circuit.