Why the Leaning Tower of Pisa is straightening up

Italy’s Leaning Tower of Pisa is half a degree straighter following decades of restorative work that has cost millions, experts have announced.

The famous Tuscan bell tower has tilted ever since it was built, in 1173, because the porous clay soil on which it was constructed is softer on the south side than the north, reports The Guardian.

But now the monument is “very slowly reducing its lean”, according to a surveillance group set up in 2001 by Professor Michele Jamiolkowski, a Polish expert in engineering, to oversee restoration work.

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Back in 1990, the iconic structure - which attracts more than five millions visitors a year - was closed to the public amid fears that it was on the verge of toppling. At the time, it was tilting by 4.5 metres (14ft 9in) from the vertical, says the BBC.

It finally reopened 11 years later, following extensive restorations that saw the tilt corrected by 45cm(17.7in) , at a cost of £200m.

Since then, the monument - a symbol of the power of the maritime republic of Pisa during the Middle Ages - has been straightened by a further 4cm (1.6in), the surveillance group has found.

“What counts is the stability of the tower, which is better than initially predicted,” said Nunziante Squeglia, a geotechnics professor at the University of Pisa who works with Jamiolkowski’s team.

“It’s as if it has had two centuries taken off its age,” added surveillance group member Professor Salvatore Settis, of the Italian Academy for Advanced Studies.

The new data shows that the tower is in good health and should be stable for at least 200 years, according to Gianluca De Felice, director of the Opera della Primaziale Pisana, the institution in charge of the monuments in Pisa’s Square of Miracles.

“We can express cautious optimism,” he told CNN.