What metaphors are used in When Nietzsche Wept by Irvin D. Yalom?

Venice becomes a metaphor for retreat and discovery. The novel begins in Venice where Breuer has gone for a break from his stressful schedule. He visits Venice again during Freud's hypnotism at the end of the book. Whereas at the beginning Venice was a place of retreat, at the end it is a place where he feels lonely and out of place. This contrast helps Breuer to realize that he doesn't want to escape his life after all.