An annual report on the monument’s stability has revealed that the tower had spontaneously recovered some of its vertical incline-straightening by 2.5 cm since 2001. The straightening is not a miracle, but the long term effect of an 11-year restoration project completed in 2001.
Previously the 56-metre bell tower’s tilt was increasing by more than a millimetre a year creating a danger that it could collapse altogether. In 1993 it was leaning by 5.4 m, compared to 3.8 m in 1817 and just 1.4 m in 1350.
The 14,500-tonne tower was shut for a decade while the foundations were reinforced and water was drained from beneath. Supporting steel cables were placed in circles around the structure.
After the £25 million
(Rs 246 crore) project, the tower straightened itself almost immediately by 38 cm. The 2013 study by a scientific committee tasked with monitoring the celebrated building confirmed ‘that the bell tower is stable but tending to straighten’.
Giuseppe Bentivoglio, technical director of the monument, said the tower’s lean towards the south is shrinking. The structural engineer explained, “The tower is moving. It is straightening towards the north. Between 2001 and 2013 it has recovered 2.5 cm of its incline.”
Bentivoglio claimed the move was ‘expected’. “According to studies by researchers at Stuttgart University with whom we worked, the tower will continue to straighten another couple of millimetres and then stabilise before starting to lean again, but at a much slower rate than before.”
He added: “In theory it would be possible to straighten it completely.” The tower brings in six million visitors to Pisa every year with three million buying tickets to climb its eight floors. Mayor of Pisa, Marco Filippeschi said: “The people of Pisa are delighted that the tower has been restored but not that it has been straightened.”
All about the Tower
Number of years it took to build the tower
The amount the tower was leaning by in 1993
The amount the tower was leaning by in 1817
Number of tourists who visit the tower