THE LEANING TOWER
Many art historians believe that the Leaning Tower was designed and begun to build by the well-known Pisan architect and sculptor Bonanno Pisano (active from 1170 ca. to 1186 ca.), while others attribute it to Magister Diotisalvi, an eminent architect of the age, who started in 1152 the construction of the magnificent Baptistery in Piazza dei Miracoli.
In 1185 ca. when the third order of the tower was completed, the building caused an initial lean towards the southwest of approximately 5 cm, because the foundations of the massive Tower had been set in a depth lesser than three meters in an inadequate, unstable soil.
The work was halted until 1272 ca. Its continuation was entrusted to the prestigious Pisan architect Giovanni di Simone who constructed other three orders with an opposite inclination. Giovanni di Simone demonstrated and exceptional skill being able to reduce the leaning of the Tower, which by the time was more than 90 cm. In 1284 the Tower had already a height of 48 meters and six orders of loggias had been completed, but the work was interrupted once more time due to the intense struggles between the Republic of Pisa and the Republic of Genoa, which culminated with the defeat of Pisa’s fleet in the decisive Battle of Meloria (6th August 1284) generating a significant loss of power to the city.
The bell-chamber topping the six orders of loggias was ended in 1372 by the eminent architect and sculptor Tommaso di Andrea Pisano, son of the most celebrated Andrea.
He also improved the correction of the axis, reducing the load on the side that was leaning, which became fixed until the first decades of the 19th century. Later, the Tower kept on leaning approximately 1 mm each year.
Since then up till 1990 new measurements of the Leaning Tower were done to determine the inclination of the foundations, as well as several engineering interventions were made trying to find a solution.
In 1990 the Tower was closed to the public, as it was believed to be almost on the verge of collapse. It was straightened by 45 centimetres returning to the position it had in the 19th century.
To dig the soil the Tower was secured with steel cables and 600 tonnes of lead weights. Afterwards, was started the straightening work of the building. More than 70 tonnes of earth from the northern side of the structure were extracted from the subsoil, producing its sinking on that side. In December 2001, after having also restored the entire stonework of the Tower, it was reopened to the public.
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Visit also in Details:
Piazza dei Miracoli -Piazza dei Cavalieri -Pisa Baptistery - The leaning Tower - Pisa
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