Bigelow Pharmacy (414 Sixth Avenue; 473-7324), the oldest apothecary in the country, has built its reputation on terrific service and an unparalleled range of prescription drugs kept constantly in stock. But much more fun than buying medicine at Bigelow is picking up treasures for your bath, like a sleek silver bottle of Claus Porto bath gel that will fill your tub with wild pansy-scented bubbles, or a Kimono soap hand-wrapped in Japanese paper. Every hard-to-find indulgence you could want is under this roof, except the exceptional Kiehl's product line. The 148-year-old Kiehl's pharmacy (109 Third Avenue; 677-3171) is still hard to beat for friendly service and generous samples, and the basic, often unscented products will always appeal to the classicists among us. If, however, you crave heavenly scents, head over to L'Occitane (locations throughout the city). Its signature fragrance manages to be both understated and wildly sexy. Besides, fiddling with the vintage-inspired tin tubes amid the chintz tablecloths and lavender sachets at these classy little shops will make you feel like you're in Provence.