Those Boulevards are perpendicular to each other and cross at the limit between the 5th and the 6th area, the Boulevard Saint Michel being this frontier. That's where the shops are quite numerous and interesting, with a young and laid back atmosphere. This is the area of the universities (La Sorbonne), that could explain also the number of bars and cafés, and bookshops. Take a walk in some little typical streets around, like Rue de la Harpe, Rue de la Huchette and Rue Saint Séverin.