The greeks used it in medicine, and the Romans mixed it into wine. During the Middle Ages the iris root, when added to water, was used like soap to wash hands and scent clothing. These days iris essence, which was once coveted by Egyptian pharaohs in the Nile Valley and is now cultivated in Florence, Italy, is turning up in unusual new fragrances like Prada's Infusion d'Iris, which debuts this month. The basis of the symbol of the city of Florence, the typically heavy-scented flower comes in about 300 varieties that can cost from $70,000 to $170,000 for a mere kilo of absolute essence. Steep price tags didn't stop Miuccia Prada from choosing it as the heart of her eau de parfum, which boasts additional notes of Sicilian mandarin, earthy galbanum, lentisc from the Mediterranean and incense for a sensual sweetness. But to prevent the infusion from becoming too sugary, notes of vetiver and cedarwood "corrupt" the fragrance unexpectedly, according to Daniela Andrier, the nose who worked with Prada. The name Infusion was inspired by the ancient, six-months-long process of drawing fragrance essence from the root of the iris plant.