Coleridge's "Kubla Khan" is an allegory of the creative process that bubbles up beneath the surface inside those people who have been touched by the deeper creative and imaginative muse of poetic genius.
In the first stanza, we see the pleasant surface of an average person's life, which encompasses the ordinary imagination of the ordinary individual. This imagination is fruitful enough: it brings forth gardens, contains an incense-bearing tree, and has "sunny spots of greenery."
In the second stanza, however, we learn that something more powerful lives inside the soul of the creative genius. This is where Coleridge begins to emphasize the emotional intensity of a deeper, more profound poetic space by using exclamation points. On this creative level, we move beyond gardens and sunny green spots to a powerful waterfall that crashes and explodes against the rocks in a "tumult." It is a place that includes prophecies of war, where fire and ice come together:
A sunny pleasure-dome with caves of ice!
This region of creative genius is far more dangerous and exciting than the placid surface imagination.
In the third stanza, Coleridge moves to visualize his poetic muse as a "damsel with a dulcimer." If he could revive her song, his own poetic genius would flow forth and build the world of imagination (the sunny dome and caves of ice):
Could I revive within me
Her symphony and song,
To such a deep delight ’twould win me,
That with music loud and long,
I would build that dome in air,
That sunny dome! those caves of ice!
Finally, coming to a crescendo, the poet expresses how this muse would display itself in him in ways that would fill people with "dread," for they would know he had drunk to the depths the sweet, powerful, and dangerous "paradise" of artistic creation.