Coleridge wrote “Kubla Khan” primarily in iambic meter. (Recall that iambic refers to a rhythmic pattern built from iambs, which are metrical feet with one unstressed syllable followed by a stressed syllable, as in the word “to-day.”) Though Coleridge generally sticks to iambic rhythm, he uses different line lengths throughout the poem, ranging between three feet and five. “Kubla Khan” is therefore made up of a mix of iambic trimeter, tetrameter, and pentameter. The poem opens with an emphasis on iambic tetrameter, as can be seen in the first five lines:

In Xan- / a-du / did Kub- / la Khan
A stat- / ely plea- / sure-dome / de-cree:
Where Alph, / the sa- / cred ri- / ver, ran
Through ca- / verns mea- / sure-less / to man
   Down to / a sun- / less sea.

The first four lines of this passage are perfectly regular iambic tetrameter. Only in the fifth line does Coleridge introduce variation, first by substituting a trochee (stressed–unstressed) in the initial foot, and second by featuring a shorter, three-foot line. The focus on iambic tetrameter gives these lines a gentle sing-song quality that subtly affirms how the vision of Kubla Khan and his “pleasure-dome” are essentially figures of the speaker’s own imagination. By ending with a line of iambic trimeter, Coleridge further emphasizes the ballad-like feeling of the poem’s opening, since ballad stanzas typically alternate between four- and three-foot lines.

After these opening lines, however, Coleridge begins to mix up the meter in less predictable ways. Consider the rhythmic changes in the rest of the opening stanza (lines 6–12):

So twice / five miles / of fer- / tile ground
With walls / and tow- / ers were gir- / dled round;
And there / were gar- / dens bright / with sin- / u-ous rills,
Where bloss- / omed man- / y an in- / cense-bear- / ing tree;
And here / were for- / ests an- / cient as / the hills,
En-fold- / ing sun- / ny spots / of green- / er-y.

Here the meter returns to tetrameter, but only for two lines. In line 8, Coleridge adds a fifth foot and expands the line to pentameter. This expansion is foreshadowed in line 7, where Coleridge introduces a three-syllable foot known as an anapest (unstressed–unstressed–stressed). The introduction of an extra syllable here offers a suggestion of excess. It’s as if the speaker’s dream is growing more detailed and thus requires more space in the speaker’s imagination. Coleridge continues to suggest this excess by using additional anapests in lines 8 and 9. In addition to suggesting the expansion of the speaker’s own vision, the shift to pentameter also has a distinct effect on the sound of the verse. Leaving behind the sing-song quality of tetrameter, the move toward pentameter gives the language a more measured and dramatic feel. It’s as though the meter conveys a greater sense of seriousness as the speaker’s vision fills out and perhaps feels more real. Coleridge sustains the use of iambic pentameter for the next eighteen lines, before eventually returning to tetrameter, possibly evoking the process of beginning to wake from a dream.