The Old Bridge At Florence

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.