A communiqué today from the Prefecture of the Pontifical Household stated that the Holy Father, accepting the invitation of Bishop Raffaello Martinelli of Frascati, will celebrate Mass in Piazza San Pietro in that Italian town on July 15.
After the Mass, the Pope will return to Castel Gandolfo where he will pray the midday Angelus.
Frascati is between Rome and Castel Gandolfo, a bit to the east.