"art desolate..."See in text(Ode on a Grecian Urn)
The urn itself is a symbol of both life and death: life in the timelessness of its art and death in the intended use of the urn (ashes). By presenting images of joy and sacrifice on the urn, Keats tells the reader we can’t have joy without despair, we can’t have life without death, and the immortality of art means it must withstand both forever.
"To what green altar..."See in text(Ode on a Grecian Urn)
This stanza suggests that the narrator is looking at a different side of the urn, considering a different aspect of the painting. The speaker specifically calls the altar “green” to tell the reader it is an actual image, not merely a figurative altar. That being said, sacrifice can be understood here as serving a figurative function, symbolizing that art is not simply eternal happiness, but also eternal pain.
"Heard melodies are sweet, but those unheard
Are sweeter..."See in text(Ode on a Grecian Urn)
Here Keats presents both a double entendre and a paradox. Keats is comparing the silence through which the urn tells its stories to the sounds he imagines coming from the pipes painted on the urn. To Keats's speaker, the silence is "sweeter."
"What men or gods are these..."See in text(Ode on a Grecian Urn)
Literally speaking, the speaker is addressing the art on the urn. However, taking into account the previous lines that address the urn’s ability to tell stories, the speaker is pleading for the urn to answer questions about life, death, and art. The speaker wishes to uncover what the urn has learned during its extended time on earth. With these questions, Keats establishes the dialectic between art and its audience as a means to discover truth, a main theme of this poem.
"unravish'd bride of quietness..."See in text(Ode on a Grecian Urn)
In the first line the speaker addresses the Grecian Urn as the “unravish’d bride of quietness,” suggesting the object he admires cannot literally speak. Using personification to address the urn communicates the importance of the archaic object to the speaker and to the poem itself.
"a parching tongue..."See in text(Ode on a Grecian Urn)
Keats compares the effects of "breathing" or mortal passions with a disease whose symptoms include fever ("a burning forehead"), dehydration ("a parching tongue"), and a broken heart. The word "cloy'd" also suggests that human passion is sappy or overly sweet, where the immortal love on the urn is timeless and refined.