The patron of Grottaferrata is Saint Nilus of Rossano, celebrated on 26 September: in 1004 he founded the Abbey of Santa Maria, under the protection of the Counts of Tusculum.
The abbey, a territorial exarchate still led today by Basilian monks, celebrates its liturgies according to the Greek-Byzantine rite; the town also holds a historic fair, documented since the second half of the 15th century.