Tower of Pisa: history and characteristics

For its beauty, history and fortune, the Tower of Pisa was named a World Heritage Site in 1987. This monument, conceived as a bell tower, is framed in the Romanesque style of the Italian Middle Ages. It is located in the place that the writer Gabriele D'Annunzio (1863-1938) once called "the square of miracles", in Pisa, Tuscany, Italy.

The tower of Pisa began to lean as soon as its construction began. However, this not only did not stop the determination and pride of that city, but more than 800 years later, the tower still stands next to the cathedral or Duomo of Pisa, affirming itself as a true architectural miracle. The "square of miracles" is completed with the Baptistery and the Campo Santo.

The construction process took about 200 years. This was due, in the first place, to the technical difficulties they encountered on the way, because of their inclination. Second, to the political and military conflicts of those years that diverted attention and resources to other companies. Let's learn more about the history and characteristics of the Tower of Pisa.

Characteristics of the tower of Pisa

Contrary to what its name suggests, the tower was built to house a free-standing monumental bell tower, intended to accompany the cathedral. This tower, which should have been completely straight, has a slightly arched shape in the opposite direction to its angle of inclination.

The building was conceived as a cylindrical tower, divided into eight levels, formed by the base, six loggias or floors, and the bell tower. In this, seven bells tuned with the main notes of the musical scale (do, re, mi, fa, sol, la, si) were installed.

The bell tower is accessed through a single door, topped with a tympanum with three figures. The interior is surrounded by two walls of limestone and marble.

Hollow inside, in the tower there are only spiral staircases with 273 steps leading to the bell tower. In the first levels, the steps are made of marble, a material that was installed during the Middle Ages to receive the nobles who visited the tower.

As is typical of Romanesque art, the base walls are extremely wide and massive, which explains its enormous weight. These walls narrow and lighten as the tower reaches greater height.

Aesthetic elements

For the decoration of the building, the architects applied marble inlays of different colors with geometric motifs.

You can also see elements of relief on the surface, both abstract and figurative (animals, human figures, floral motifs, among others).

The columns are grouped in different amounts depending on the level. At the base there are a total of 15 columns that order a succession of blind semicircular arches. The six intermediate loggias have a gallery of 30 columns each, while the bell tower, which corresponds to the eighth level, has a gallery of 12 columns.

All columns support semicircular arches. They are smooth shafts and are topped with decorated capitals. You can see some capitals with volutes and acanthus leaves that reveal the influence of Greco-Roman art. But you can also see some with motifs such as mythical or fantastic creatures that reflect the mentality of the Romanesque, still in force in Tuscany at that time.

Measurements of the tower of Pisa

The tower measures the following:

• An approximate height of 55.8 meters, although it was conceived to reach 60 meters.
• An approximate outside diameter of 15.4 meters.
• An inside diameter is 7.36 meters.
• A weight of 14,700 tons.
• Current tilt angle approximately 5º.

Stages of construction

It is not clear who is the author of the original project of the bell tower. Some suggest that it was Diotisalvi (Deustesalvet), who was building a section of the Baptistery at that time. Vasari suggested that it would have been Bonanno Pisano, but this attribution appears to be wrong. It is known, yes, that the tower was supervised by Giovanni Di Simone.

First stage, from 1173-1178

It was in August 1173 that construction work began on the Tower of Pisa. In this period, the base and the first three floors or loggias of the tower are raised. However, at this point the tower begins its process of inclination towards the north.

The cause will be in two key factors. The first of them is related to the characteristics of the soil. The site was loamy and sandy. This was because the area had been a recovered swamp, the first cause of instability.

The second aspect had to do with the architectural project. Indeed, the base of the building was barely 3 meters deep, which was insufficient to locate the tower on a terrain of similar characteristics.

With no immediate solutions to come up with, it was decided to stop construction for the first time in 1178.

Second stage, from 1272-1278

Almost a hundred years had to pass before the project was taken up again. It will be from the year 1272 that the fourth floor is completed and more levels are added, which were arranged in an opposite slope in order to correct the imbalance.

By then, the tower had reached an approximate weight of 9.5 tons. But this time, the tower began to lean the other way, heading south. To contain this process, they placed heavy materials in the northern section, an insufficient strategy to straighten the building, so work was interrupted again in 1278.

Third stage, from 1360 to 1370

Construction work on the tower was restarted in 1360, which represents about 82 years of waiting. This last effort made possible its culmination in 1370. The tower reached its final shape with the final finish of the bell tower.

Safeguarding efforts

Many have been the efforts to avoid the collapse of the Tower of Pisa. Various commissions have been formed throughout history in order to find the best solution. In this regard, Enrique Santoyo and Efraín Ovando report in a text entitled Parallelism between the Tower of Pisa and the Cathedral of Mexico, what:

The history of the commissions in charge of the safeguarding of the Tower of Pisa is very long. It could be said that the first dates back to the year 1298, when the experts of the time met to discuss the resumption of construction. In 1840 the Second Commission began to study the inclination and in 1907 the Third. Since then, leading geotechnical engineers have participated, including C. Trevisan, A.W. Skempton, S. Marchetti, A. Kezdi, G.A. Leonards, C. Viggiani, J.B. Burland and M. Jamiolkowsky. K. Terzaghi (1934) also made a study of the Tower.

Some of the alternatives attempted only exacerbated the problem, sinking and tilting the tower further. To this was added that, in 1944, a bombing in World War II almost destroyed it.

Over time, efforts to protect the monument were resumed. Santoyo and Ovando comment that in 1972 a competition was called by the Italian government to protect the tower without its inclination having to be corrected.

The dispute to correct or not the inclination had begun. Despite this, any position for or against faced an incontestable reality: could leave the tower as it was, as it ran the risk of collapsing, nor could it be straightened totally.

It would not only be inadvisable to straighten the tower completely, but impossible. This is because the tower is not totally straight but slightly arched in the shape of a "banana". Straightening her would make her lean to the opposite side.

Understanding this, it was necessary to close the tower to the public for eleven years for corrective and preventive works. In that period, they managed to reduce the incline from 5.5º to 5º, which is an extraordinary step. Today, the tower of Pisa is once again open to visitors from all over the world.