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The Tower of Pisa

The Leaning Tower of Pisa may be the most instantly recognizable building in the Western world, with the possible exception of the Eiffel Tower. It is a part of a complex of three buildings, consisting of a baptistery, a church, and the bell tower that form the Cathedral of Pisa.

The Tower of Pisa was constructed in three stages over a period of almost 200 years. The construction began in 1173, but by the time the third level was finished, it was already tilting badly, because of the soft sand and clay beneath its foundations. Fortunately, however, the construction of the tower was halted for almost a century due to battles between Pisa and its nearby regions. The standstill let the soil settle and keep the tower for the following centuries. After a long interruption, construction was resumed in 1272, with engineers building subsequent floors with one side higher than the other to compensate for the tilt and was completed between 1360 and 1370.

For years, however, anxious city fathers measured the tower and found it leaning a fraction of an inch further every year. Nevertheless, the tower has withstood several mild earthquakes and extensive bombing in World War II. Benito Mussolini tried to have it straightened entirely in the 1930s, but the concrete poured into its foundation only made it sink further, thus perpetuating Pisa's claim to tourist fame.

In 1964, the government of Italy requested aid in preventing the tower from toppling. A multinational task force of engineers, mathematicians and historians gathered to discuss stabilisation methods. Many methods were proposed to stabilise the tower, including the addition of 800 tonnes of lead counterweights to the raised end of the base. The structure was declared a World Heritage Site by Unesco in 1987.

In January 1990, after over two decades of stabilisation studies, the tower was closed to the public, when it was found to be nearly 15ft off the vertical. The bells were removed to relieve some weight, and cables were cinched around the third level and anchored several hundred meters away. Apartments and houses in the path of the tower were vacated for safety. The final solution to prevent the collapse of the tower was to slightly straighten the tower to a safer angle, by removing 38 cubic meters of soil from underneath the raised end. The tower was straightened by 45 centimeters, with the angle of the tilt being decreased from 5.5 degrees to about 3.99 degrees. On December 15, 2001, after a decade of corrective reconstruction and stabilization efforts, the tower was reopened to the public.

Y et there was more work to be done. There were cracks so large in the top of the columns that a person was able to put an entire hand inside them. The stones were in an appalling state, mainly due to air pollution, though tourists and pigeons played a part. The columns of the tower are decorated with capitals: flowers, ghoulish faces, fantastical animals, but sea salt carried on the wind and rain water that collects in certain areas because of the tower's tilt had damaged many stones.

When the works began restorers took out the concrete used in past restorations and cleaned up the pigeon dirt, graffiti and hand-prints left by tourists. They injected chemicals into the marble to strengthen it. Then they cleaned the surface with water sprays, solvents and even lasers for delicate spots.

Mountaineers scaled the tower and attached hanging, aluminium platforms. Traditional scaffolding could’ve unsettled the soil under the newly stabilized tower. The mountaineers were tied to an upper level and linked by ropes. As work progressed from level to level, the workers would hand each other the pieces to construct a new level of scaffolding while taking apart the scaffolding below, all the while suspended in the air. This scene fascinated tourists who were basically watching these crazy people spinning around and climbing up and down.

And there was interior work too. For an entire winter, restorers toiled on the tower’s internal staircase during chilly nights, to allow tourists to visit during the day – tourists who bring in receipts of up to $30,000 a day — funds needed for the restoration and upkeep. In May 2008, after the removal of another 70 metric tons of earth, the Italian engineers announced that the Tower had been stabilized and that it had stopped moving for the first time in its history. They stated it would be stable for the next 200 years.

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