Note 1 : Coleridge notes : “This fragment with a good deal more, not recoverable, composed, in a sort of Reverie brought on by two grains of opium, taken to check a dysentery, at a Farm House between Porlock and Linton, a quarter of a mile from Culbone Church, in the fall of the year 1797.” 

Coleridge also indicates that he was inspired by travel literature, particularly Samuel Purchas, Purchas His Pilgrimage (1613), in which we read: ‘In Xamdu did Cublai Can build a stately Palace, encompassing sixteene miles of plaine ground with a wall, wherein are fertile Meddowes, pleasant springs, delightfull Streams, and all sorts of beasts of chase and game, and in the middest thereof a sumptuous house of pleasure...’

Alph : The River Alpheus is in Greece, and known for the fact that part of its course is underground.

Mount Abora: the 1797 version has ‘Mount Amara’ : see Milton :

Nor where Abassin kings their issue guard,
Mount Amara, though this by some supposed
True Paradise, under the Ethiop line,
By Nilus’ head, enclosed with shining rock
A whole day’s journey .........

Milton: Paradise Lost, Book IV, line 280 and following.