What is the mood of ode on a grecian urn?

I do not know of any special story related to Keats Ode on a Grecian Urn, but the poem was written in 1819 and many critics have assumed it was partly influenced by Keats' visits to see the Elgin Marbles which the British Government had bought in 1816.

Lord Elgin's removal of sculptures from the Parthenon was as controversial then as it is now. Elgin argued that since the Turkish army was using the Parthenon for gunnery practice it was better to remove the sculptures to London where they were safe.

Many people though thought that the sculptures belonged where they had originally stood, even if that led to their destruction.