This is the oldest religious building in the Montefeltro area and bears witness to its conversion to Christianity. The term parish refers to the community of this massif that St. Leo evangelized between the 3rd and 4th centuries. According to tradition, it was the saint himself who built the first church here. Rising high above the sheer rock, the façade faces east and can be entered via two side portals, both topped by a small blind loggia and with alternating two-coloured ashlars, a precise reference to Byzantine-Ravenna art. The columns and capitals were reclaimed from the Roman or late Antique periods. The candid ciborium with heavily sculpted capitals (881-882) is particularly precious.