In "Kubla Khan," Coleridge describes two types of imagination. First, there is the ordinary imagination of the average person, who, in the first stanza, conjures up pleasant images of incense, gardens, and "sunny spots of greenery" in a lovely kingdom.
In the second stanza, the speaker moves to the deeper poetic imagination of the artist and prophet. This goes beyond the mere pleasant and pretty and explodes into powerful sexual imagery of waterfalls, a "romantic chasm," "fast thick pants," and the "burst" of a "mighty fountain." This is a deeper, more forceful, potent, and dangerous imagination.
Although this is a dangerous place, it is also a visionary place, offering the speaker a "music" like none other. He says at the end of the poem that he has fed on "honeydew" and "drank the milk of paradise" because, despite his "holy dread," he has braved his fears to immerse himself in this deeper, prophetic world of the artist's imagination.