A real pearl of the Adriatic coast, in the province of Ancona (Le Marche), just off SP1 there is Mazzavalle. Access is only really possible by car, there are buses that run nearby but they are infrequent. Google Maps will guide you there easily, upon reaching the car park head down the hill. Warning: the hill is very steep and can get quite slippery. Take some decent shoes with you for the trek up and down, it will take about 10-15 minutes. Once you reach the bottom in the bay, go left down to the end where you will find the unofficial nudist area. The rest of the beach is normal. Since it is in a bay sheltered by cliffs the sun will only be out until about 6pm but the bay really catches the sun in the morning.