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.
So twice five miles of fertile ground
With walls and towers were girdled round :
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.
Coleridge claimed he wrote the poem after experiencing a vision during an opium-induced sleep, but was woken by a ‘person from Porlock’ before it was complete.
Coleridge’s biographer, Richard Holmes, suggests that because we tend to remember dreams best when we’re woken in their midst, rather than cutting short the poetic inspiration, the ‘person from Porlock’ may have actually saved this vision from sinking into the depths of unconsciousness.
However, it’s not clear whether the vision genuinely occurred as Coleridge claimed, so this remains speculation.
If you’re interested in a more in-depth analysis of this poem that Coleridge called a “a psychological curiosity”, there’s an excellent article in the PsyArt journal that examines it using a number of cognitive and psychological theories.