Roman Churches are (mostly) free art galleries. Their opening times can be erratic, but, if you plan well or you are just fortunate, you can wander in off the street and stand before some amazing works of art; paintings, frescoes, sculptures and mosaics.
Santa Maria del Popolo (Two Caravaggios and a Carracci in the Cerasi Chapel)
San Luigi dei Francesi (More Caravaggios including the incomparable Calling of St Matthew)
Sant’Agostino (Caravaggio’s Madonna di Loreto)
San Pietro (Michelangelo’s Pietà)
LET THE SWANS COME FORWARD 