Another way to look at La Dolce Vita is to think of Marcello's journey (played by Marcello Mastroianni) as the cinematic version of the Book of Daniel which describes the "Apocalypse" or Revelation: a disclosure of something hidden from the majority of mankind in an era dominated by falsehood and misconception. The film begins with the imagery of Christ flying over Rome as a helicopter carries a religious statue aloft over the city -- or visions of Angels. Marcello's journey includes encounters with the "Great Whore" (Sylvia, played by Anita Ekberg), the suicide of his close friend whose life has descended into despair, a Judgment of the wicked (the orgy at the villa), the Beast (symbolized by the manta ray/devil fish on the beach), the purity of the virginal young girl who beckons to Marcello to save him but he chooses the decadent life -- viewed in this way, the film has a layer of symbolism that deepens it.
Who is  the "Great Whore"?
Sylvia