Nature
Nature was a very prominent focal point in Romantic literature. Coleridge uses a very detailed element of nature throughout the entire poem. In the first stanza he speaks of Kubla Khan's decree to build a "pleasure palace" and then describes the paradise that will surround it by using images of nature.
"And there were gardens bright with sinuous rills, Where blossomed many an incense-bearing tree; And here were forests ancient as the hills, Enfolding sunny spots of greenery."
Imaginative Vision
Coleridge was an opium addict and in a drug-induced slump he dreamt of himself writing a poem, Kubla Khan. When he woke up he began to write down the poem he saw in his dream. Due to the origin of the poem it has a very imaginative tone to it. Coleridge was visited while writing down what he remembered and when he went back to writing he had forgotten everything that followed what had already been written.
"Kubla Khan Or, a vision in a dream. A Fragment"