In a poem called "Eldorado," we should expect to hear a whole lot about… Eldorado, right? And that we do—at least, sort of. The speaker doesn't tell us too much about what Eldorado might look like, only that the knight has been searching for a long time and, even by the end of his life, hasn't found it. While Eldorado at first seems to be a real place, by the end of the poem we feel that it represents something else, some dream or hope—an idea about life—that the knight is unable to achieve. And in the end, poof! It's just a shadow, something unrealistic (which might be why "Eldorado" and "shadow" are rhymed throughout the poem).