The prophet Ezekiel writes, "I have set Jerusalem in the midst of the nations, and countries are round about her" (Ezekiel 5:5). Taken in its plain sense, the verse places the holy city at the exact center of the inhabited world. The early Christian scholar Jerome, centuries later, still knew this idea well enough to call Jerusalem umbilicus mundi, the navel of the earth. The image was Jewish long before it was anything else.
The Talmud translates the picture into an anatomy lesson. Issi ben Yochanan, reporting in the name of Shmuel Hakatan, taught: the world is like the eyeball of a human being. The white of the eye is the ocean that surrounds all dry land. The black of the eye is the landmass itself. The pupil, the dark circle at the center, is Jerusalem. And the image reflected in the pupil, the small figure you see when you look closely into another person's eye, is the Temple.
The prayer that ends the passage is not a decoration. It is the whole point. "May it be rebuilt in our days, and in the days of all Israel, Amen." (Derech Eretz Zuta 9).
Jerusalem is not the center of the earth by geography. It is the center the way the pupil is the center of the eye: the small point through which everything else is seen.