John Keats' "Ode on a Grecian Urn" uses many literary devices, including symbolism, allegory and imagery. Many of the devices pertain to either the titular urn or the prominent natural setting of the poem.
The urn takes on different symbolic values as the story's speaker turns it in his hands and examines the different imagery on the sides. Before he examines the sides, he thinks of the urn as a virginal bride, and afterwards as shapely but overwrought. Ultimately, he treats it like a wise man that has wisdom for the speaker to absorb. By having the speaker examine the different aspects of a single object, Keats can better transmit his message that truth and beauty are one and the same, even when the notions of both truth and beauty are relative.
The speaker also has a complicated relationship with the plants and vegetation of the poem. On a surface level, Keats uses this setting to highlight the poem as pastoral. However, the speaker eventually becomes overwhelmed by the abundant nature around him and believes that it serves as a distraction from the simple beauty of the urn itself. Because the urn's beauty derives partially from its simplicity, Keats symbolically urges readers to see past intoxicating distractions in order to discover something truly beautiful.