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Why does 'Leaning Tower of Pisa' lean ?

Updated on January 2, 2013

The Leaning Tower of Pisa

One of the Tower Bell's (Assunta Bell)

Syringe Technique used for cleaning

Engineers Plan

Plaque in the memory of Galileo Galilei

Prof. John Burland

'The Leaning Tower of Pisa' is one of the world's most beautiful buildings. It is the bell tower of the cathedral of Pisa, a city in Italy. The whole building is made up of white marble and Romansque in style.

The height of the tower is 55.86 m from ground on lower side and 56.70 m from the ground on the higher side. It leans 14 feet from vertical and continues to lean farther south every year. Its construction was started in 1174, which was considered as Pisa's golden age. The tower was to surpass all the building in Italy at that time and to mark the wealth and prosperity of Republic of Pisa.


It took 177 years for the tower to be built into full shape. It was done in 3 stages.

  1. In the first phase, ground floor was completed and construction progressed to the second floor. But, the tower began to sink due to weak three -meter laid on unstable soil. Construction was stopped for almost 100 years.
  2. The second phase of construction resumed in 1272 and was halted in 1284, when Pisan's were defeated in the 'Battle of Meloria'.
  3. The third phase was all about finishing the seventh floor and installing the seven bells one for each floor.

Why does the tower lean?

It leans because when the building second floor was in construction, the soil under one half of the circumference began to sink and the tower started to tip . The architects, when they started the construction in the second phase, they devised a plan to compensate the tilt. The first two floors were built normally, third and fifth floor were built out of line with other floors and closer to vertical in order to maintain the towers center of gravity. The tower continued to lean gradually through the centuries.

Restoration Work:

There were many attempts made to suppress the tilt of the tower, like

  • Pumping to keep the water away from the foundation.
  • Injection of cement grout in to the foundations.
  • Placing lead weights on the north side of the tower.
  • The major restoration work was done between 1990 and 2001. Chisels, hi-tech laser technology and syringes were used to clean each and every single stone in the structure.
  • The stabilization part was completed in 2008. Around 70 metric tons of earth was removed from underneath the taller part of the tower. It is now, a lot straighter and leans 3.99 degrees when compared to 5.5 degrees previously. The estimated cost was around 25 million USD.
  • After the stabilization was done, the engineers confirmed that the tower stopped moving for the first time in the history and will be stable for at least next 200 years.

Some Facts:

  • The famous astronomer and physicist Galile conducted his experiments from the top of the tower and proved that bodies of different weight fall at the same speed.
  • The square where the tower is located is known as "The Square of Miracles". The name given by an Italian poet who called it "Prato dei Miracoli".
  • The square was declared a UNESCO World Heritage Site.
  • The tower has seven bells, one for each musical major scale.
  • Prof.John Burland, was one of the main men who worked hard for two decades understanding the construction of the "Leaning Tower of Pisa" and his expertise helped the tower from collapse.

Though the tower has experienced lots of calamities during its lifetime, it has not collapsed and continues to amaze the crowd . It is one of the major tourist attractions in the world. The tourists are now allowed to the climb the staircase inside the tower after the restoration was finished. It is still an icon of Pisa.


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    • profile image

      Raj Samala 6 years ago

      nice and informative information... thanks for sharing -

    • mightylearning profile image

      mightylearning 6 years ago from Minneapolis

      Thanks Nare !!

    • Nare Anthony profile image

      Nare Gevorgyan 6 years ago

      Wow! I love this hub. Soo interesting and informative. Thanks for sharing :)

    • mightylearning profile image

      mightylearning 6 years ago from Minneapolis

      Thanks a lot. Hope you read more from me.

    • Bldg an Architect profile image

      Bldg an Architect 6 years ago

      This is a great hub. You really packed in a bunch of info. I'm probably a little biased since I'm an architecture geek, but I think its awesome!