Leaning Tower of Pisa Timeline

(1173 - Present)

The Leaning Tower of Pisa is a freestanding bell tower (campanile) of Pisa Cathedral in Italy. Begun in 1173, it became famous for its unintended tilt caused by soft ground on one side of its foundation. Despite nearly collapsing over the centuries, the tower was stabilized through engineering interventions in the late 20th and early 21st centuries and remains one of Italy's most iconic landmarks. More Less

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Construction and Design

Donna Berta di Bernardo bequeaths funds for the tower

Jan 5, 1172

On 5 January 1172, Donna Berta di Bernardo, a widow and resident of the house of dell'Opera di Santa Maria, bequeathed sixty soldi to the Opera Campanilis petrarum Sancte Marie, providing early funding for the tower's construction.

Foundations of the tower are laid

Aug 9, 1173

On 9 August 1173, the foundations of the Leaning Tower of Pisa were laid, beginning one of the most famous architectural projects in history.

Work begins on the ground floor

Aug 14, 1173

Work on the ground floor of the white marble campanile began on 14 August 1173 during a period of military success and prosperity for the Republic of Pisa.

Vasari later credits Guglielmo and Bonanno Pisano

1174

Nearly four centuries later Giorgio Vasari wrote: "Guglielmo, according to what is being said, in the year 1174, together with sculptor Bonanno, laid the foundations of the bell tower of the cathedral in Pisa." The design had long been attributed to Guglielmo and to Bonanno Pisano, a well-known 12th-century resident artist of Pisa known for his bronze casting.

Tower begins to sink after second floor is built

1178

The tower began to sink after construction had progressed to the second floor in 1178, due to soft ground which could not properly support the structure's weight. This marked the start of its famous lean, which would worsen through the completion of construction in the 14th century.

Construction halted amid wars with Genoa, Lucca, and Florence

1178

Construction was subsequently halted for the better part of a century, as the Republic of Pisa was almost continually engaged in battles with Genoa, Lucca, and Florence.

Bonanno Pisano leaves Pisa for Monreale, Sicily

1185

Pisano left Pisa in 1185 for Monreale, Sicily, only to return and die in his home town. He had been credited with the tower's design alongside Guglielmo.

Image source: Bonanno Pisano

Benenato oversees continuation of construction

Dec 27, 1233

On 27 December 1233, the worker Benenato, son of Gerardo Bottici, oversaw the continuation of the tower's construction after the long wartime hiatus.

Guido Speziale elected to oversee building

Feb 23, 1260

On 23 February 1260, Guido Speziale, son of Giovanni Pisano, was elected to oversee the building of the tower.

Image source: Leaning Tower of Pisa

Giovanni di Simone leads marble-cutting expedition

Apr 12, 1264

On 12 April 1264, the master builder Giovanni di Simone, architect of the Camposanto, and 23 workers went to the mountains close to Pisa to cut the required marble for the tower.

Construction resumes under Di Simone

1272

In 1272, construction resumed under Giovanni di Simone, continuing the tower's slow progress despite its ongoing lean.

Construction halted after Battle of Meloria defeat

1278

Construction was halted again in 1278 when the Pisans were defeated by the Genoese in the Battle of Meloria, interrupting work on the tower once more.

Image source: Battle of Meloria (1284)

Tower survives earthquakes thanks to soil-structure interaction

1280

The tower has survived at least four strong earthquakes since 1280. A 2018 engineering investigation concluded that it withstood the tremors because of dynamic soil-structure interaction: its height and stiffness combined with the softness of the foundation soil prevent it from resonating with earthquake ground motion.

Seventh floor completed

1319

The seventh floor of the tower was completed in 1319, bringing the structure closer to completion more than a century after construction began.

Bell-chamber added, completing construction

1372

The bell-chamber was finally added in 1372, completing the tower's construction roughly two centuries after its foundations were laid. The lean had worsened through the entire construction period due to the soft ground beneath the structure.

Largest bell installed in the tower

1655

The largest of the tower's bells was installed in 1655, adding to the campanile's collection of historic bells.

New bell installed to replace broken Pasquareccia

1790 - 1799

A new bell was installed in the bell tower at the end of the 18th century to replace the broken Pasquareccia.

Cast bearing Bonanno Pisano's name discovered

1820

A piece of cast bearing Bonanno Pisano's name was discovered at the foot of the tower in 1820, but this may be related to the bronze door in the façade of the cathedral that was destroyed in 1595.

Study suggests Diotisalvi was original architect

2001

A 2001 study seems to indicate Diotisalvi was the original architect, due to the time of construction and affinity with other Diotisalvi works, notably the bell tower of San Nicola and the Baptistery, both in Pisa.

Image source: Diotisalvi

Scientific and Cultural Significance

Bell tolled for execution of Count Ugolino

1289

The tower's bell was tolled to announce executions of criminals and traitors, including Count Ugolino in 1289.

Image source: Ugolino della Gherardesca

Galileo reportedly drops cannonballs from the tower

1589 - 1592

Between 1589 and 1592, Galileo Galilei, who lived in Pisa at the time, is said to have dropped two cannonballs of different masses from the tower to demonstrate that their speed of descent was independent of their mass, in keeping with the scientific law of free fall.

Viviani writes biography recounting Galileo's experiment

1654

The primary source for Galileo's famous experiment is the biography Racconto istorico della vita di Galileo Galilei, written by Galileo's pupil and secretary Vincenzo Viviani in 1654, though it was only published in 1717, long after his death.

Image source: Vincenzo Viviani

Piazza del Duomo declared UNESCO World Heritage Site

1987

The tower and the neighbouring cathedral, baptistery, and cemetery were included in the Piazza del Duomo UNESCO World Heritage Site, which was declared in 1987.

Image source: Piazza dei Miracoli

Capital Gate certified as world's furthest leaning tower

Jun 2010

Two German churches had challenged the tower's status as the world's most lopsided building: the 15th-century square Leaning Tower of Suurhusen and the 14th-century bell tower of the Oberkirche in Bad Frankenhausen. In June 2010, Guinness World Records certified the Capital Gate building in Abu Dhabi, UAE as the "World's Furthest Leaning Man-made Tower"; it has an 18-degree slope, almost five times more than the Tower of Pisa, but was deliberately engineered to slant.

Image source: Capital Gate

850th anniversary of foundation stone laying celebrated

Aug 9, 2023

A ceremony for the 850th anniversary of the laying of the foundation stone was held on 9 August 2023, marking eight and a half centuries since the tower's construction began in 1173.

Stabilization Efforts

Italy requests aid to prevent tower from toppling

Feb 27, 1964

On 27 February 1964, the government of Italy requested aid in preventing the Leaning Tower of Pisa from toppling over.

Tower closed to the public

Jan 7, 1990

By 1990, the tilt had reached 5.5 degrees. The tower was closed to the public on 7 January 1990, after more than two decades of stabilisation studies and spurred by the abrupt collapse of the Civic Tower of Pavia in 1989.

Lead counterweights added to straighten the tower

1993

Starting in 1993, 870 tonnes of lead counterweights were added, which straightened the tower slightly as part of the remedial stabilization work that continued until 2001.

Tower reopens to the public after restoration

Dec 15, 2001

After a decade of corrective reconstruction and stabilization efforts between 1993 and 2001, which reduced the tilt to 3.97 degrees by removing 45 centimetres of tilt and returning the tower to its 1838 position, the tower was reopened to the public on 15 December 2001 and declared stable for at least another 300 years.

Engineers announce tower has stopped moving

May 2008

In May 2008, engineers announced that the tower had been stabilized such that it had stopped moving for the first time in its history. After a phase (1990–2001) of structural strengthening, the tower has been undergoing gradual surface restoration to repair visible damage, mostly corrosion and blackening.

Key Facts

Construction began on August 9, 1173, but stopped after just five years due to wars, taking nearly 200 years to complete in 1372.
The tower's famous lean started during construction because of soft soil and a shallow foundation on one side of the structure.
The tower stands about 56 meters (186 feet) tall and has eight stories, including the bell chamber at the top.
In the late 20th century, engineers reduced the tilt from about 5.5 degrees to roughly 4 degrees using soil extraction, stabilizing the tower for at least another 300 years.
The Leaning Tower of Pisa is part of the Piazza dei Miracoli (Square of Miracles), designated a UNESCO World Heritage Site in 1987.

Source

This Leaning Tower of Pisa timeline was generated with the help of AI, using information found on the internet.

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