Leaning tower is finally saved from collapsing

For centuries, on the eve of the feast of its patron, Saint Ranieri, the city of Pisa comes alight. As the red summer sun drops low in the sky, mansions, bridges and churches are lit up by thousands of candles in tribute to the pious nobleman who returned victorious from the Crusades to dedicate himself to Pisa's lepers. Tonight's vigil will be more symbolic than most for the inhabitants of this industrious town.

In an official ceremony the keys of the Leaning Tower will be handed back to the city after an 11-year project to save the tilted monument from collapse. The world-famous marble masterpiece ­ finally freed of braces, lead weights and steel cables ­ is expected to reopen to the public later this year.

When it was closed in haste in 1990 as its lean increased by 1mm a year, it was four-and-a-half metres off centre. Today the 800-year-old marble cylinder, immortalised in countless tourist snaps, is just over 4m off centre, its masonry has been reinforced and, says the committee of experts, the bell tower is safe for another 250 years.

With just hours to go before the handover ceremony, the project's manager, Paolo Heiniger, a solidly built Milanese man with a silver moustache, leads the way up the 293 footworn marble steps to the summit of the bell tower. He points out the discreet metal braces that still surround the second storey. "This is one of the most delicate segments of the tower, especially this south side, most at risk from actual structural collapse," he says.

Atop the tower, alongside the seven bells, flies the red flag of Pisa. Behind stand the Pisan mountains, from whose now-defunct marble quarries the material for the Tower was excavated. Below us the splendour of the dazzling white baptistery and the elegant Duomo. It is a view that has been off limits except to a handful of experts for more than a decade. "It is a great joy but also a huge relief to be finishing," admitted Mr Heiniger, who directed all the workmen on one of the world's most delicate engineering projects.

Did Mr Heiniger or any of the committee of scientists responsible for the salvation of the tower ever lob lead balls over the side, like their illustrious ancestor Galileo? "No, we're a little beyond that," Mr Heiniger chuckled, "but if we did you could be sure they would land 4.1 metres from the base, which is precisely the distance that the tower is off-centre. The photos will still be identical. No human eye could notice the straightening that has taken place nor indeed can you feel it inside." But the gentle easing has put the two threats ­ that it might tip over, or that it might buckle under its own weight ­ on hold.

At the tower entrance, is John Burland, Professor of Soil Science at Imperial College, London, one of the 14 member committee who shouldered the responsibility of fiddling with one of the world's best loved and most delicate buildings.

"I imagine it's like finishing a marathon. For so long you have been checking your stopwatch, eyeing your opponents and looking for the water bottles, then suddenly you're at the finishing post," he said.

The 11-year project has been dogged by controversy, criticism and, above all, fear. When it was closed, the tower was at risk, so the first priority was finding ways to prevent damage while a more permanent solution was sought.

In 1992, the tower was surrounded by braces of 18 steel wires at the level of the first storey. This reinforced the masonry to head off the risk of structural failure due to the sheer stress of the lean on the foundations. From 1993-5 on the side away from the lean, blocks of lead, reaching up to 800 tonnes, were attached as a counterbalance.

Then came what became known in Pisa as Black September. Workmen were freezing the ground beneath the tower to limit vibration when they discovered an undocumented circle of concrete dating from the 19th century. During the night of 7 September, 1995, the tower lurched 1.5mm. "It was one of the worst moments of all but we had steel stays attached to ensure it did not fall," said Professor Burland.

In the 11 years since the monument has been closed to the public, Italy has had 11 governments, approved 15 decree laws regarding financing the recovery project and spent 55billion lire. Italian government bureaucracy did not help the experts who were often deeply divided. As the committee members, 12 Italians and two foreigners, thrashed out possible solutions, they eventually opted for the most simple ­ as the tower leaned towards the south, they would extract soil from under the north side, helping to decrease the lean. Yet for a terrain with "the consistency of jelly or foam rubber to a greath depth" it was a highly risky business.

Forty-one tubes were inserted to a depth of six metres to suck out the soil; first tentatively with real-time monitoring then as the tower responded well, in greater quantities.

Gloomy forecasts that the 1990 closure of the tower would have sent Pisa's tourist-based economy into a nosedive have proved competely unfounded.

Public access is the next big issue. A committee will examine how and when that can happen. Professor Burland said letting people back up "will have negligible impact on the structure, though there are some colleagues who are opposed to this". It is expected that only groups of 25-30 will be go up at a time, from October, and the ticket price is set to rise to 25,000 lire (£8).

In Pisa, there is a climate of excitement and pride as they prepare to celebrate the recovery of "their tower".

As the red carpet was being put out and the television satellite vans were lining up for tonight's ceremony, the beautifully proportional square which contains the Cathedral, the Baptistery and the Monumental Cemetery was throbbing with tourists. Elena, a curly-haired politics student adorned with piercings, said: "Try to understand how it would be to live with the fear that the very symbol of your city, like the Tower of London, might just collapse. Can you imagine what that would do for the collective consciousness?"

An Italian adage says that "any student who hopes to graduate shouldn't risk climbing to the top", but Elena swore she would be one of the first up there when it opened.