Campanile di San Marco
A number of threats during the 9th and 10th centuries drove Venice to erect a series of fortifications to protect the city from invasion by sea. This even included a wall, no longer extant, just east of the Palazzo Ducale, though its exact location has been lost to time. An iron harbor chain was also implemented, which could be pulled taut across the Grand Canal in order to block ships from navigating into the city that way. In addition to this, construction on a watchtower began during in the 10th century, using bricks dating from the Late Roman Empire, taken from nearby ruins. Construction continued, adding height to the tower, until it was crowned with a first belfry that was added in the 12th century, itself crowned by a pyramidal wooden spire sheathed in copper.
A reconstruction replaced the belfry after it was burned by lightning in the late 14th century, again done in wood, though the copper plates used were this time covered in gold leaf. This allowed the tower to be seen from the Adriatic, and to be used to guide Venetian ships safely into harbor. Further incidents kept the Venetians reconstructing the belfry over the course of the 15th century, and Giorgio Spavento was commissioned to create a design to rebuild it in masonry once and for all. Its high cost, however, prevented the city from completing the project until 1511, after an earthquake shook the tower and the integrity of the structure was severely compromised. Finally, the tower was completed in 1514, reaching its final height, and was crowned with a weather vane in the shape of the Archangel Gabriel. A lightning rod was installed on the structure in 1776 — the first in Venice — under the urging of the physicist Giuseppe Toaldo.
A loggetta (or a small “loggia,” a covered portico) was added to the structure in the 15th century. It was to serve as a gathering place for nobles and the procurators of Venice as they conducted their business, and as a sentry post for the Palazzo Ducale. In the 16th century, after many years of rebuilding due to damage from falling pieces of the tower itself whenever lightning struck, Jacopo Sansovino was commissioned to completely rebuild the structure. The new loggetta was completed in 1546.
As early as 1885, it was discovered that the base of the tower was in poor condition, but reports by architects and engineers in 1892, and again in 1898, claimed that the tower was not in danger. As such, any restoration work completed in this period of time was superficial at best. In 1902, work was underway to restore the loggetta, but where structural support leaned against the tower, it began to form a fissure, roughly 40cm (16in) in height and 30cm (12in) in depth. As a new support was installed, there were reports that the tower trembled. Elements used in order to determine the shifting of a building were then installed in the structure, and found broken the next day. Barricades were installed to keep onlookers away from the tower as pieces of mortar began to break off the tower and fall into the square. The bells, which formerly rang out the beginning, pause, and end of the work day, were rung only once, at the end of the day, to limit vibrations to the structure.
On July 14th, 1902, the latest tell-tale elements installed were found broken. At 9:30am, the square was ordered evacuated, with stones beginning to fall by 9:47am. By 9:53am, the entire structure had collapsed. The loggetta was completely demolished, and though the isolated nature of the tower kept the damage to surrounding structures to a minimum, a corner of the Libreria Marciana was destroyed, as was a porphyry column from the basilica. After emergency sessions to determine a course of action, the communal council formed for this crisis decided that the tower would be rebuilt as it had stood previously. The new main structure was completed in 1908, with construction on the belfry and attic beginning the following year. Work began on the spire in 1911, and the new tower was officially completed in 1912.
Today, you can ride an elevator (a 1962 addition) to the tippy top of the tower and feast your eyes on these gorgeous views of the city.
The bells of the tower have been historically used to mark the stages of the work day as well as the times of day. Whenever there were government assemblies or public executions, the bells were also used to call on the citizenry. Only one bell survived the collapse of 1902. Today, a system in which the rope that swings the bell is wrapped around a grooved wheel was instituted, in order to minimize vibrations and thus damage to the tower.