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After 11 years and remedial works costing $27 million, the world-famous Leaning Tower of Pisa reopened to the public 15 years ago today, on December 15th, 2001.

Engineers and architects had been working continuously since 1990, not to remove the tower’s famous lean, but to prevent it getting any worse and inevitably toppling over. Making the tower safe was paramount, but so was preserving its gravity-defying lean – the unintended feature which draws tourists from around the globe to marvel at Pisa’s most remarkable attraction. 

The 190ft white marble tower was built in the 12th century as the bell tower for the cathedral of Pisa, a busy trade centre on the Arno river in central Italy. Obviously its designers never meant it to lean, but almost from the start it refused to oblige their best efforts to make it stand upright.

Soft, marshy ground at the tower’s foundation caused one side of its base to start sinking even while construction was in progress. Frantic efforts were made to shore it up, but the noticeable lean could not be reversed. The builders then tried to compensate for it by making the top storeys of the tower slightly taller on one side, so they would at least appear upright.

Unfortunately, the weight of the extra masonry only made the tower sink further and the lean worsen. By the time the tower was completed in 1360, people coming to view it were amazed it hadn’t already toppled over. Although the cathedral itself and the adjoining baptistery also leaned slightly, it was far more obvious in the tall tower which soon became known as the “Torre Pendente de Pisa” – the Leaning Tower of Pisa.

Careful monitoring revealed the lean was increasing slightly each year so that by the 20th century the top of the tower was a dramatic 15 feet off the perpendicular and, claimed many experts, on the brink of collapse. The situation wasn’t helped by the ever-growing number of tourists keen to climb the tower’s 293 steps and gaze from the top across the ‘Campo dei Miracoli’ – the Field of Miracles. Of course they all wanted to stand on the leaning side!

Finally, in 1990 the decision was taken to close the tower for safety reasons and begin work to halt its incline. The previous year a million visitors had climbed the precarious pinnacle!

A handpicked group of 14 highly experienced engineers, architects and soil experts was assembled to figure out how to reverse some of the tower’s tilt and stabilise it for future generations. First the bells were removed to reduce the weight at the top of the tower. At the same time, high-tensile steel cables were secured around the tower’s third level and anchored to the ground several hundred metres away.

As a safety precaution, houses and apartments in the shadow of the tower were evacuated during the works. The chosen solution was to remove more than 1,300 cubic feet of earth from underneath the raised side of the tower and at the same time stack tons of lead counterweights around that side of its base. It was hoped this would encourage the raised side to gradually sink into the cavity created beneath it, helped along by continually tightening the supporting steel cables.

Despite a few heart stopping moments, the process slowly began to work, so that after a decade the lean had been reduced by 45cms, returning the tower to its 1838 position. With that level of lean considered acceptable, work then began to stabilise the tower, before its bells were finally put back in place.

When it reopened to the public on December 15th, 2001, it was declared stable for at least another 300 years. By 2008, after seven years of painstaking monitoring, it was officially announced that the tower had stopped moving for the first time in its 650-year history.

Even so, entrance to the tower is now restricted to guided tours, with an annual limit on the number of visitors allowed to ascend it. The classic tourist photo these days involves standing in the foreground of the tower and striking a pose so that it appears you are holding up the tower, like the one pictured here.

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