The correct answer is that these lines talk about the immortality of art.
Ode on a Grecian Urn by John Keats is often interpreted as the celebration of art and its immortality. The figures depicted on the urn have passed long before the narrator examines the urn on which their lives were depicted. Even though they perished their story has been preserved on the urn, and in a sense they have become immortal through the art, which is that which remains long after we are gone.
