The poem itself mentions "dancing rocks" which are "vaulted like rebounding hail" or "chaffy grain beneath the thresher's flail," which emerge from a "mighty fountain" forced from a chasm.  
The prose preface to this work quotes ten lines from "The Picture," which end with a passage about some "fragments dim of lovely forms" which come "trembling back, unite, and now once more / The pool becomes a mirror."  The poem itself mentions "dancing rocks" which are "vaulted like rebounding hail" or "chaffy grain beneath the thresher's flail," which emerge from a "mighty fountain" forced from a chasm.  In a less tumultuous section, it refers to some "gardens bright with sinuous rills" where "many an incense-bearing tree" are blossoming.  Later, we learn of a song of Mount Abora which is chanted by a "damsel with a dulcimer," and the speaker claims that if he could revive her song within him he would "build that dome in air."  FTP, name this poem which features a sacred river named Alph and a "stately pleasure-dome" decreed in Xanadu by the titular Mongol ruler, a work by Samuel Taylor Coleridge.
The prose preface to this work quotes ten lines from "The Picture," which end with a passage about some "fragments dim of lovely forms" which come "trembling back, unite, and now once more / The pool becomes a mirror."  
"Kubla Khan"