First of all, Nino Rota's divine soundtrack. Someone said it is the music of nostalgia.
Tonino Guerra, a great poet, and his screenplay. He also wrote Tarkovsky's Nostalghia
The voyage at night toward the Rex returning from America, one of the most magical scenes ever made in cinema. Gradisca's confessions, the blind man playing his accordion and asking "how is it"- the starry sky.
The discreet death of the mother, Pupella Maggio, one of the greatest Italian theater actresses of the twentieth century.
The night "passeggiate" in Fellini's invented village at Cinecittà, the closed stories, the movie theater, the main square, the balconies.
The joy, freedom, fear, and magic of youth, and the end of magic with Gradisca's wedding.
One wonders where such deep reactions to a film come from.