The Power of Art
Closely related to the poem's ideas about aging, mortality, and the soul is its treatment of art.The elderly speaker, having left behind the world of the young which no longer has room for him in his frailty, goes to seek spiritual rebirth in the ancient city of Byzantium--an ancient holy city that is now long-dead.As such, when he has learned from the sages and left behind his body, the speaker says, he will never "take / My bodily form from any natural thing," and describes instead taking the form of some piece of golden art. In this he might resemble one of the mosaics in which he sees the sages. But he may also take the form of a golden bird, though he doesn't say so directly: in his other vision of his immortality, he sits on a bough and sings, just as the living birds in the first stanza do.

The mortal body is left behind in the transition into immortality, but the artistic body remains: the speaker wishes to become art himself, to "sing to lords and ladies of Byzantium"--in short, to become a piece of art that might help other mortals to become a piece of art.That is, they are forever preserved via art, ageless and undying.Art, here, is presented as a pathway to immortality.