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Every year millions of tourists travel to Pisa, Italy, to see the famous leaning tower.
Despite its notorious tilt, the tower has stood for nearly 850 years, and there's
no sign it's going to fall over anytime soon. However, that wasn't always the case.
The leaning tower of Pisa was originally intended to stand straight up - designed
as a freestanding bell tower to accompany the Pisa Cathedral.
Construction began in 1173, but by the time the second floor was added the foundation began to
sink and the tower started to lean. The ground at the building site was a poor choice for a
tower - sand, clay, and mud, too soft to support the weight of the heavy marble. As one side of the
tower sank, the builders tried to compensate by making the columns on the low side taller
so that it would seem straight. Unfortunately, the extra weight only made the tower lean more.
It soon became obvious that the problems with the tower were too big to fix that way,
and construction was stopped after only five years while the architects looked for a solution.
In the meantime, Pisa went to war with Genoa and for a century the tower was abandoned.
It wasn't until 1272, nearly 100 years after it was started, that work resumed.
By then the ground under the tower had settled enough to better support its weight
and the tower was leaning south - the opposite direction!
Construction continued for 6 more years, but this time they knew the tower was going to lean.
The height of each story was tapered so that the floors at the top would be flat.
Once they completed the seventh story, building halted again.
It wasn't until 1372 that the eighth story was added,
angled north to try and balance out the southern lean, and the tower was completed.
Although contruction only lasted for about 20 years, with all the interruptions,
it took nearly 200 years from the day they began before the tower was completed!
The finished tower measures nearly 57 meters or 186 feet tall at its highest side, and about
one meter or 3 feet shorter on the opposite side. Two spiral staircases lead to the top:
one staircase has 294 steps while the other has 296 steps to compensate for the differing heights.
Over the years the tower continued to lean farther, putting it in danger of falling over.
Many people wanted to stop the tower from falling, but they didn't want to straighten it all the way
because of how many people came to see it each year.
In 1990 the tower was closed for over ten years while engineers tried to stabilize it.
First they added over 800 tons of lead weights to one side
and anchored the tower with cables to stop it from moving while they thought of something better.
They also removed the bells from the eighth floor to lighten the weight a little.
Finally they decided to remove dirt beneath one side of the tower very, very slowly
so that it would straighten up just enough to be safe.
This method reduced the tilt by over 17 inches or 45 centimeters - not enough for
tourists to notice, but enough that the tower has stopped shifting for the first time in history.
Engineers believe that it will continue to be stable for at least 200 years.
Today the bells have been replaced in the belltower
and people are once more allowed to climb the steps to the top. I hope you enjoyed
learning about the famous leaning tower of Pisa today. Goodbye till next time!