It is the bell tower of the Cathedral of Santa Maria del Fiore (Duomo), most famous monument of the city for its characteristic slope. It has been proposed as one of the "Seven Wonders" of the modern world. The foundation is attributed to Bonanno Pisano, who also designed bronze doors of the Cathedral, while the construction of the belfry to Giovanni di Simone, in the fourteenth century. Already during the construction of the tower it began to lean because of land subsidence. It is a bell tower on its own about 56 meters high and built over two centuries (XII-IVX). In the structure dominates the curved line, with rounds of blind arches and six floors of loggias. The slope is due to land subsidence occurred in the early stages of construction. The inclination of the building currently measures 3.97° from the vertical axis. Tower remains in equilibrium because the vertical line passing through its center of gravity falls within the base of support. Inside, a staircase of 294 steps leads to the top from which there is a unique show on the Square and across the city.
No admittance for children under eight years. Children between 8 and 12 must be held by the hand during the visit; children under 18 accompanied by adults.