3-D point cloud scan of the Leaning Tower of Pisa with measurements by CyArkCyArk
The Leaning Tower of Pisa was never supposed to stand at an angle. Built between 1173 and 1372 as the free-standing bell tower for Pisa Cathedral, the tower started to tilt in the 12th century when its poor foundations began sinking into the soft ground.
Italy, Tuscany, Leaning Tower of Pisa, Cathedral Santa Maria Assunta (2007-09-17) by Alexander HassensteinGetty Images
Over the years, there have been a number of attempts to right the structure. While some of these have had mixed results, others have actually made the lean worse, leaving the tower in danger of complete collapse.
[The Baptistery and Leaning Tower of Pisa] (Full Front)The J. Paul Getty Museum
Finding the Source of the Lean
The Leaning Tower of Pisa started to tilt even before it was completed. And by 1550, the top of the structure was already 12 feet south of its base. In 1838, an architect was given permission to excavate the bottom of the tower. A portion of the building had sunk below the ground and it was hoped the project would reveal the structure and provide clues to the source of the lean.
However, after digging down just a little, water began spurting out of the ground and the tower sunk a further few inches south. It’s now believed that the structure was built on an old riverbed and it’s this soft, spongy soil that responsible for its trademark tilt.
Tap to explore
Mussolini’s Masterplan
When Benito Mussolini came to power, he decided that the leaning tower wasn’t a proper symbol for the macho Italy he wanted to create and so set about straightening it. His team of engineers drilled holes into the foundations and poured in 200 tons of concrete. Rather than righting the tilt, it shifted the top of the tower even further to the south.
[Leaning Tower of Pisa] [Leaning Tower of Pisa] (about 1865) by UnknownThe J. Paul Getty Museum
Preventing Collapse
By the second half of the 20th century, the Italian government feared that the lean had become so severe the tower was in danger of collapse. It asked for suggestions on how to stabilize the building and in 1964 and 1985, two further attempts were made to drill into the foundations and keep the tower upright. However, both of these projects failed, only adding to its lean.
Leaning Tower of Pisa
The Ground Freezes Over
In 1990, the tower was closed to the public due to safety fears. In 1992, plastic-coated steel tendons were built around the tower, covering it up to its second story. The following year concrete foundations were built around the tower and counterweights placed on the north side. This project was one of the first to have a positive impact, lessening the lean by around an inch.
A few years later in 1995 the commission wanted to replace the steel tendons with underground cables. During the preparations works, the ground was frozen using liquid nitrogen. This caused the tilt to increase dramatically. See if you can right it in 3D!
Pisa; Royal Palace, San Possare (1945-05) by Margaret Bourke-WhiteLIFE Photo Collection
Stability at Last
In 1999, engineers began a new project to stabilize the tower. Soil was extracted very slowly from the north side and a cable put in place to keep the building in place. Within just six months, the tilt had been reduced by an inch and by December 2001, when it was reopened to the public, it had been righted by around 18 inches. It’s thought this will add an impressive 300 years to the tower’s lifespan.
3-D point cloud scan of the Leaning Tower of Pisa by CyArkCyArk
Learn more about the Leaning Tower of Pisa here.
