Poems employing the circular structure begin in one place, then journey away from that place, only to (as you may have guessed) circle back to the beginning. Here are a few examples:
“Man on a Fire Escape,” by Edward Hirsch (in Earthly Measures: Poems (New York: Knopf, 1994).
“The Opposite of Crunchberries,” by Jennifer L. Knox (in A Gringo Like Me: Poems (Soft Skull, 2005)).
“On Gravity,” by Mary Szybist (in Granted (Farmington, ME: Alice James Books, 2003): 39).
Because its first and third lines return in its final quatrain, the pantoum form also features the structure of a circular movement. Check some out:
And, of course, the circular structure is popular in arts other than poetry. Check out some of these examples: