The corruption of Italy: Allegory
Marcello's story of debauchery and immorality is an allegory for the corruption of Italy (and specifically, its government officials). Like Italy, its citizens, and its government officials, Marcello's life is devoid of meaning and rife with corruption.
The Trevi Fountain: Symbol
The Trevi Fountain is one of the most recognizable and important symbols in film history. It is symbolic of Marcello's significant change in his life and the changing of the tides in his life and relationships.
The statue of Jesus: Symbol
The statue of Jesus is symbolic of Catholicism and the foundations of Italian society. Historically, Italy and its society were rooted in the tenants of Catholicism. Many lived their lives according to those tenants and society, according to the film, had more meaning. How many people in Italian society are living during the setting in the film is anathema to the tenants of Catholicism.
Anita Ekberg: Symbol
Anita Ekberg, the Swedish film star who has been compared to Marilyn Monroe, is one of the most recognizable sex symbols in the history of film. And sex is one of the most powerful forces in the film. It is one of the reasons for Marcello's struggles (Anita Ekberg's character is the object of Marcello's lust and affection) and is one of the reasons for the corruption of Italian society and the Italian government.
Water: Motif
Water is a very frequent and important motif in La Dolce Vita. In the film, while Marcello and one of the many ladies who he is sexually interested in, go through their days, they invariably find themselves in water—whether it be a fountain or because of rain. Water is a powerful symbol for rebirth, life, and fertility and plays an important role in Marcello's life (and the life of other Italians).