A rhetorical question is asked for literary effect, with no actual answer expected. In "Ode on a Grecian Urn," the speaker asks a series of rhetorical questions in stanzas 2 and 4. In both stanzas, the questions are about the historical context of the events depicted on the urn.

In the second stanza, the speaker asks what legends "haunt" or inform the scene shown on the urn. Is it a story of Greek gods depicted or of mortals? Who are the people (or gods) shown on the urn? What motivates their struggles and/or happiness?

In the fourth stanza, similar questions are asked of the urn. They center on the nature of the religious festival that has brought the townspeople out of their village. Why is a heifer being led out of town laden in garlands?

In neither stanza does the speaker expect an answer to these questions, because there is none. The point is that the historical context has been lost and therefore doesn't matter. What matters is the "now" depicted on the urn, which is completely timeless. This moment doesn't need to be tied to a historic era because, being a work of art, it has stepped out of time. All that matters is the particular moment of springtime joy and youthful bliss the speaker sees, frozen forever and thus unchanging.