Taddeo Gaddi built me. I am old,
Five centuries old. I plant my foot of stone
Upon the Arno, as St. Michael's own
Was planted on the dragon. Fold by fold
Beneath me as it struggles. I behold
Its glistening scales. Twice hath it overthrown
My kindred and companions. Me alone
It moveth not, but is by me controlled.
I can remember when the Medici
Were driven from Florence; longer still ago
The final wars of Ghibelline and Guelf.
Florence adorns me with her jewelry;
And when I think that Michael Angelo
Hath leaned on me, I glory in myself.

Henry Wadsworth Longfellow

http://www.poemhunter.com/poem/the-old-bridge-at-florence/