Xanadu by Samuel Taylor Coleridge.

“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. “