The building is of white marble. The tower is divided into eight stories, each having an outside gallery of seven feet projection, and the topmost story overhangs the base about sixteen feet, though, as the center of gravity is still ten feet within the base, the building is perfectly safe.

It has been supposed that this inclination was intentional, but the opinion that the foundation has sunk is no doubt correct. It is most likely that the defective foundation became perceptible before the tower had reached one-half its height, as at that elevation the unequal length of the columns exhibits an endeavor to restore the perpendicular, and at about the same place the walls are strengthened with iron bars.