Probably the queen stage of the challenge, that won’t let you sleep the night before... Fascinating and full of pitfalls through quarries of pietra serena, chestnut groves and mythical passes like Futa and Raticosa, a path that will leave an indelible memory in your legs. Here the menu of the day: Passo del Paretaio, Pass that in 18 kilometers joins the Senio valley with the Santerno valley Narrow, very winding road with several blind curves, to be approached with caution. 5.7km average slope 6% Passo Futa from Firenzuola develops just over 11 kilometers. Leaving aside the first 4 kilometers, and more precisely up to Cornacchiaia, the most interesting are certainly the following 7 kilometers that exceed a height difference of 423 meters with peaks close to 10% From the Futa pass (mt. 903) at Passo Raticosa is a continuous ups and downs with a final hard climb that starts from the town of Pietramala. From the Raticosa pass on the ridge of about 24km towards Fontanelice passing next to the Sasso di san Zenobi, an ophiolitic rock full of legends and superstitions. Arrived at Gesso fast descent to Fontanelice, 8 very fast km, eye to the very tight curves. Once in Fontanelice you will have 2 options to reach the Prugno. Option 1, the bad one, the mythical "climb of the Dog". A couple of miles scarce, but "terrible" with peaks well over 20% and an average gradient of 13.92%. Impressive is the stretch from kilometer 1 to kilometer 1.5 that looks like a real wall, a height difference of 70 meters with sections at 22-23% A monument at the top dedicated to Marco Pantani saying "MURO DEL PIRATA" is well combined with the layout. Option 2 a little sweeter also called the road of lavender, a plant that arises spontaneously along the roadside and, particularly on the Senio side, cultivated in small gardens at the edge of the road. 6.9 Km regular, without excessive peaks. Arrived then Casola Valsenio, 16km will separate you from the end of this intense day.