The patrons of Riolo Terme are Saint John the Baptist and Our Lady of the Rosary, celebrated on the first Monday of May.
The «Feste di Maggio», the Marian month, have been celebrated uninterruptedly since the 17th century: in 1667, residents made a vow to the Madonna, asking forgiveness and protection from a terrible hailstorm that on 2 July of that year destroyed the entire harvest of the Riolo area. On a day in July, they joined in procession behind the image of the Virgin, from the parish church to a crossroads outside town, where another image of the Madonna, known as «del Presidio», was affixed on a pole; since then the procession has been repeated every year. The town also holds the Rocca di Riolo Terme and the Castello di Sassatello.
