Le Litanie della Vergine di Mario Deluigi. Dialogue between the Sacred and Abstraction

In 1949 Mario Deluigi painted an altarpiece for a Salesian church in Mogliano Veneto, and the Salesians turned it down. The panel is 220 cm square, oil and collage, built from colour, rhythm and letter forms, and subtitled Homage to Mondrian. Judged unfit for a church, it went to the 1950 Venice Biennale instead, where it drew applause and ridicule.

In 1972 the Patriarch of Venice, Albino Luciani (later John Paul I), gave it to Paul VI, who kept it in his private apartment until his death in 1978. Newly restored, it hangs with the ten screenprints Deluigi made from it, the notebook where he planned them and two Rubelli textile panels. You come for one painting and leave knowing who refused it and who took it in.

It's free with a Papal Palace of Castel Gandolfo ticket, sold on the Vatican Museums site, and closes on 15 November. A parish said no, so seeing it now takes a train out of Termini and a papal palace.