Kubla Khan by Samuel Taylor Coleridge (1816)

In Xanadu did Kubla Khan a stately pleasure-dome decree: the line arrives already chanting itself, sound running ahead of sense, and you are inside the spell before you have parsed a single word. A sacred river winds through caverns measureless to man down to a sunless sea; a deep romantic chasm slants across a green hill where a woman wails for her demon-lover; ancestral voices prophesy war. Coleridge swore the whole vision came to him entire in an opium sleep, hundreds of lines composed without effort, until a person from Porlock knocked and the rest dissolved like images on a stream after a stone is thrown in. What he saved breaks off at the instant the speaker aches to rebuild that dome in air from the half-remembered song of an Abyssinian maid. The poem cannot finish what it dreams, and that refusal is its glory: a pleasure-dome built of pure sound, sunny and caverned, already vanishing even as you read it.