The famous tower leans precariously at a five-degree angle, giving it an offset at the top of over five metres. Photo / Getty Images
The famous tower leans precariously at a five-degree angle, giving it an offset at the top of over five metres. Photo / Getty Images
The Leaning Tower of Pisa isn't leaning so much any more.
After more than two decades of efforts to straighten it, engineers say the famed Tuscan bell tower is in better structural health than previously thought and has recently recovered four more centimetres, MailOnline reports.
According to Professor Salvatore Settis, this is the equivalent of taking two centuries off its age.
A consultant to the international committee monitoring the tilt, Nunziante Squeglia, said that while the progressive recovery of tilt is good news, the overall structural health of the tower is more important.
In 1987 the Tower of Pisa was declared a World Heritage Site by the United Nation's cultural organisation Unesco, but as fears grew that it would topple over it was closed to the public in 1990 and engineers worked to stabilise it for the next 11 years.
The 12th-century tower was reopened to the public in 2001 and remained open throughout a restoration costing over $11million - partly to keep tourists happy, but partly because the revenue from ticket sales helped pay for the upkeep. The tower attracts over one million visitors a year.
By using hundreds of tons of lead counterweights at the base and extracting soil from under the foundations, engineers initially shaved 43 centimetres off the lean.
The tower's famous lean appeared about five years after construction began in 1173, and before the structure was finished.
The clay and sand below the tower is far softer on the south side than the north, and had already started to shift when the builders were working on the third of the tower's eight stories.
This resulted in the now-iconic defection in the tower, but initially it meant construction was paused with only the first three stories completed.
After a 90-year hiatus, engineers restarted work on the tower and built the additional floors diagonally in an attempt offset the tilt.
Further disruptions meant the completion of the structure - a symbol of the maritime might of the republic of Pisa - was delayed until 1372, a full 199 years after it began.
Just seven miles from the Mediterranean Sea on the west coast of Italy, the tower, which weighs some 14,500 metric tonnes, is frequently battered by storms that have eroded and discoloured it.
But it has proved sturdy enough to withstand at least four powerful earthquakes that have rocked the Tuscany region in central Italy.
The Leaning Tower of Pisa is a popular attraction for tourists visiting Italy. Photo / Getty Images
The distinctive, yellowish stone came from the quarries of San Giuliano, visible from the top of the tower on the green hills behind Pisa.
Experts say the seven-storey bell tower should now be safe from further intervention for at least the next 200 years.
How did the Leaning Tower of Pisa get its tilt?
The famous tower leans precariously at a five-degree angle, giving it an offset at the top of over five metres.
Yet the 58-metre tall, eight-storey tower has managed to survive, undamaged, at least four earthquakes that have hit the region since 1280.
Construction of the tower began in 1173, and five years later it began to sink, when building had progressed to the third floor.
The cause was a flawed design - it had a foundation that was only three-metres deep set in weak, unstable subsoil.
Back then that area of Italy was very belligerent, with various local land-grabbing factions jostling for position.
Because of the battles between Pisa and nearby Genoa, Lucca and Florence, the construction of the tower was put on hold for almost a century.
Thankfully this allowed enough time for the soil to settle - had there not been that length of break, many believe the tower would have toppled over centuries ago.
When tools were picked up once more, under architect Giovanni di Simone (who had built the Camposanto Monumentale, the fourth and last building to be erected in Cathedral Square) in 1272, the engineers built upper floors with one side taller than the other, in an effort to compensate for the tilt.
Because of this, the tower is actually curved. Construction was halted again in 1284, when the Pisans were defeated by the Genoans in the Battle of Meloria, and the seventh floor was not completed until 1319. Its stewardship at that point had passed to Tommaso di Andrea Pisano.
Finally, the bell-chamber was finally added in 1372.
