Xanadu was a reference to the summer capital of the Yuan dynasty of China, mentioned in Samuel Taylor Coleridge's poem Kubla Khan: 'In Xanadu did Kubla Khan, a stately pleasure-dome decree.' ...
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 ...