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Last edited 14 Dec 2018
Stabilising the Leaning Tower of Pisa
The Leaning Tower of Pisa is the freestanding bell tower of the cathedral of the Italian city of Pisa. Famous for its unintended tilt, the 56 m tower took nearly 200 years to build - work started in 1173. Five years later it started tilting.
Work completed in 2001 saw the tower straightened by 38 cm.
A 2013 study found that 'the bell tower is stable but tending to straighten' and that it had moved a further 2.5 cm vertically since 2001.
The structure is expected to straighten another couple of millimetres and then start to lean again – but at a much slower rate.
The method – known as soil extraction – saw engineers dig a series of tunnels on the north side of the tower and remove small amounts of earth. (The tower leans to the south.) Steel cables helped pull it back into its original position.
 Fascinating facts
There are other buildings that lean more than the Tower of Pisa. The Capital Gate building in Abu Dhabi, UAE is the world's most tilted man-made tower. It has an 18-degree slope – 5 times more than Pisa – although it was deliberately constructed to slant.
This article was originally published here in 2018 by ICE.
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