Five Little-Known Facts About the Leaning Tower of Pisa

The Leaning Tower of Pisa has got to be one of Italy's most recognizable tourist photo opportunities. Each year, more than 5 million people visit the tower, hoping to snap the perfect picture of themselves with the monument. The world-renowned tower firmly puts the city of Pisa on the tourist map. While the image of this tilting tower is recognizable worldwide, how much do you know about the 850-year-old monument? Test your knowledge as we list 5 lesser-known facts about the Leaning Tower of Pisa. 1. It's not the only leaning tower in the world. Despite being the most famous leaning tower, the Leaning Tower of Pisa doesn't even make it into the world's top 3 most leaning buildings. According to the Guinness World Records, the Capitol Gate Tower in Abu Dhabi is the farthest-leaning manufactured building, having been purposely designed to lean, achieving an angle 5 times greater than that of the Tower of Pisa. Other famously angled towers include the Leaning Tower of Surhuzen, the previous record holder, San Martino Vescovo Church in Burano, Italy, Tsuyumbike Tower in Kazan, Russia, and Church of Our Beloved Ladies by the Mountain in Bad Frankenhaus in Germany. Not only is the Leaning Tower of Pisa not the only leaning building in the world, but it's also not even the only one in Pisa. Other famous leaning buildings in the town include the Campanile di San Nicola, which only has a slight tilt, and the Campanile di San Michele degli Scalzi, which has a more noticeable leap. 2. It is a bell tower. The name the Leaning Tower of Pisa clearly wasn't assigned to the tower when its construction began in 1173. While its original name has been lost, it was likely referred to as the Campanile di Pisa as it was built to serve as the bell tower for Pisa Cathedral, with Campanile meaning bell tower. Although the bell tower construction started in the latter half of the 1100s, war halted construction for nearly a century. As a result, the bell chamber was not added until 1372, 199 years after construction began. Because the tower had already gained its characteristic lean by this point, the two spiral staircases that lead from the ground to the bell tower are slightly different heights, with one having two extra steps to compensate for the height difference. Over the next three centuries, seven bells were added to the tower, each sounding a note of the musical scale. Currently, the tower bells are Assunta, which is the largest and was cast in 1654, Crocofiso, which was originally cast in 1572 and was recast in 1818, San Regneri, originally called Gestizia, Dal Pozzo, meaning from the well, cast in 1606, Pascherizia, which was cast in 1262 and originally hung in the Tower of Bogata in Palazzo Pretorio, where it was also initially called La Gestizia, Terza, meaning third, cast in 1473, and Vesprucio, meaning twilight, which was recast in 1501. Each bell used to be rung for a particular moment. La Gestizia bells, which translates to justice bells, would be rung to announce the execution of traitors. Pascherizia would sound at Easter, and other bells would ring to mark the time of day, such as Terza, which would indicate the third hour of the day, spanning three hours from 6 a.m. to 9 a.m., and Vesprucio, which would sound at 6 p.m. to mark the sunset evening prayer called Vespers. Galileo did not use the tower to demonstrate that acceleration due to gravity is independent of mass. Galileo Galilei was born in Pisa in 1564. He grew up to be a famous mathematician, astronomer, and philosopher, whose contributions to science are still celebrated today. One of his most famous achievements was disproving Aristotle's commonly accepted theory of gravity, which held that heavier objects would fall to earth faster than lighter ones. Galileo theorized that if two objects were the same size, a difference in weight would not affect the falling speed, so both objects would hit the ground at the same time. According to legend, Galileo proved this by dropping two cannonballs of differing weights from the top of the Leaning Tower of Pisa. Both cannonballs landed simultaneously, disproving Aristotle's theories once and for all. This legend has been widely accepted and is often repeated as fact. However, many now believe that this tall tale was the invention of Galileo's biographer, Vincenzo Viviani. While Viviani attributed this physical experiment to Galileo, no evidence supports it. Many now assert that dropping cannonballs off a tower was nothing more than a thought experiment, albeit one that resulted in a factual outcome. Galileo actually had a more practical way to demonstrate his theory, and one that did not involve carrying cannonballs up the 251 steps to the top of the Leaning Tower of Pisa. He made a groove in a board, which he polished and lined with smooth parchment. He then raised one end of the board and rolled a hard, smooth ball of bronze down the groove. He could then time how long it took for the ball to roll various distances. It was called the inclined plane experiment, and it demonstrated that the acceleration of the falling object was not proportional to the mass of the object, but to the angle of the inclination. Galileo was not the first to dispute Aristotle's theory of gravity. One of the first was John Philoponus, a Byzantine Greek philologist during the 6th century BCE, who performed falling experiments using unequal weights. In 1586, three years before the given dates of Galileo's Leaning Tower experiment, a young Flemish mathematician named Simon Steven and Jan Cornets de Groot, a Dutch nobleman, dropped two lead balls of different weights from a church tower in the Dutch city of Delft. The pair recorded that both balls landed simultaneously, but the experiment did not receive much attention at the time. So why was this experiment attributed to Galileo and the Tower of Pisa? Well, probably largely due to Galileo being native to Pisa, but it was ultimately down to Viviani, who was a student of Galileo and greatly admired him in his work. The first recorded mention of the story of Galileo ascending to the top of the Leaning Tower of Pisa came 15 years after his death. The story may have resulted from Viviani wanting to glorify his mentor and give Galileo a legendary tale, dramatizing his contribution to science. If this is the case, he most certainly achieved his goal, as the story might be the most famous act attributed to this great mathematician. However, Galileo's method of using ramps would have been much more effective as it would have slowed down the rate of acceleration enough to properly measure it, and it eliminated factors of human error. Despite many attempts to straighten it, the tower was destined to lean from the start. The freestanding bell tower was the last structure in the cathedral complex to be built. It was designed to be 185 feet, or 56 meters, tall, eight stories, and made of white marble. Unfortunately, the architect did not account for Pisa's soft soil, which consists of clay, fine sand, and shells. The building's foundations began settling unevenly, and after the construction of the third story, the building had already started to lean. Around this time, construction had to be halted due to a war that broke out between Pisa and the city-state of Genova that lasted almost 100 years. Historians now believe that this pause in construction gave the foundation sufficient time to settle properly, and it is likely that, had the tower been completed as planned, it would have collapsed. When construction resumed, the engineer in charge, Giovanni De Simone, tried to compensate for the tilt by making the rooms on the sunken side slightly taller. Unfortunately, this exacerbated the issue, as the extra weight of the masonry caused the tower to sink even more. Construction continued, but every attempt to correct the tilt was ultimately unsuccessful. Since the tower's completion, almost all efforts to improve the building have resulted in worsening the lean. In 1838, architect, engineer, and Pisa native, Alessandro della Garadesca, tried to add value to the tower by uncovering its beautifully carved base, unintentionally contributing to the tilt. In 1934, Italian dictator Benito Mussolini decreed that the tower was an embarrassment and should be straightened. Feeling that the leaning tower was inappropriate for the masculine image he wanted fascist Italy to convey, he ordered that holes be drilled into the foundation of the building for around 200 tons of concrete to be poured into the base. Not only did this not achieve the desired straightening of the tower, but it also caused it to lean several more inches to the south. In the 1950s, the lean was such a cause for concern that the heavier bells were silenced, as it was believed that the swinging bells could potentially make the lean worse. In the 1960s, another attempt to stabilize the structure was halted as the tower tilted another fraction during the drilling, and the same thing happened in 1985. Due to safety concerns, the tower was closed to the public in 1990. During the early 1990s, steel tendons and counterweights managed to lessen the tilt by an inch. The success did not last long, and when they sought to hide the counterweights underground in 1995, the tower's lean dramatically increased when engineers tried freezing the ground with liquid nitrogen in preparation for digging in the weights. The stabilization project finally succeeded in 1999 when engineers began extracting soil from under the north side of the tower. Massive cables held the building in place in case of a sudden collapse, and the soil was removed very slowly to reduce the risk of destabilizing the structure. By the following year, the project managed to right the tower by nearly a foot, and in December 2001, the Leaning Tower of Pisa was once again open to the public. Despite its precarious lean, the Tower of Pisa has been able to withstand major earthquakes, as well as all the misguided attempts to straighten it. Engineers have long been puzzled by the tower's ability to withstand earthquakes undamaged, especially since it is known that there have been at least four strong earthquakes in the region since 1280. Given the precariousness of the tower, which has leant at roughly a five-degree angle since its construction, it is not surprising that a research team of engineers sought to explore this phenomenon. In the mid-2010s, researchers determined that the soft soil responsible for the tower's unstable lean had actually helped the tower withstand the quakes. Due to a phenomenon known as DSSI, or Dynamic Soil-Structure Interaction, the combination of the soft soil and the stiff structure caused the vibrational characteristics of the tower to be modified. Incredibly, this means that the tower does not resonate with the earthquake ground motion. It has been determined that the Leaning Tower of Pisa has the world record in DSSI effects. Ironically, the very thing that has caused the tower to lean has helped it remain standing for over 800 years. If you know any more interesting facts about the Leaning Tower of Pisa, please tell us in the comments below. How would you like to get a deeper understanding of history? Impress your friends and predict the future more accurately based on past events? If this sounds like something you might be into, then check out the brand new Captivating History book club by clicking the first link in the description. 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