In an opium infused sleep, Coleridge dreamed. He dreamed of a place far away, both in space and time. A place of splendor. Paradise.
It was in Mongolia during the 13th century that Kublai Khan built his summer palace. He surrounded that palace with an immense walled garden. A place from which he founded the Yuan dynasty and ruled China as a foreigner.
It was into that garden that Coleridge's imagination traveled. And from those travels his poem Kubla Khan 
emerged. One that would give voice, perhaps more clearly than other piece, to the new Romantic sentiment that he and Wordsworth were pioneering.
A garden he called Xanadu.
Within that garden a sacred river flowed, what he called the Alph:
>In Xanadu did Kubla Khan A stately pleasure-dome decree : Where Alph, the sacred river, ran Through caverns measureless to man Down to a sunless sea.
A river from which genius flowed, forced through a chasm into a moment of meaning:
>And from this chasm, with ceaseless turmoil seething, As if this earth in fast thick pants were breathing, A mighty fountain momently was forced: