The Leaning Tower of Pisa or simply the Tower of Pisa is the campanile, or freestanding
bell tower, of the cathedral of the Italian city of Pisa, known worldwide for its unintended
tilt to one side. It is situated behind the Cathedral and is the third oldest structure
in Pisa's Cathedral Square after the Cathedral and the Baptistry. The tower's tilt began
during construction, caused by an inadequate foundation on ground too soft on one side
to properly support the structure's weight. The tilt increased in the decades before the
structure was completed, and gradually increased until the structure was stabilized by efforts
in the late 20th and early 21st centuries. The height of the tower is 55.86 metres from
the ground on the low side and 56.67 metres on the high side. The width of the walls at
the base is 2.44 m. Its weight is estimated at 14,500 metric tons. The tower has 296 or
294 steps; the seventh floor has two fewer steps on the north-facing staircase. Prior
to restoration work performed between 1990 and 2001, the tower leaned at an angle of
5.5 degrees, but the tower now leans at about 3.99 degrees. This means that the top of the
tower is displaced horizontally 3.9 metres from where it would be if the structure were
perfectly vertical.
Architect There has been controversy about the real
identity of the architect of the Leaning Tower of Pisa. For many years, the design was attributed
to Guglielmo and Bonanno Pisano, a well-known 12th-century resident artist of Pisa, famous
for his bronze casting, particularly in the Pisa Duomo. Bonanno Pisano left Pisa in 1185
for Monreale, Sicily, only to come back and die in his home town. A piece of cast with
his 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. However, recent
studies seem to indicate Diotisalvi as 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. However, he usually signed his works and there is no signature
by him in the bell tower which leads to further speculation.
Construction
Construction of the tower occurred in three stages across 199 years. Work on the ground
floor of the white marble campanile began on August 14, 1173, during a period of military
success and prosperity. This ground floor is a blind arcade articulated by engaged columns
with classical Corinthian capitals. The tower began to sink after construction
had progressed to the second floor in 1178. This was due to a mere three-metre foundation,
set in weak, unstable subsoil, a design that was flawed from the beginning. Construction
was subsequently halted for almost a century, because the Republic of Pisa was almost continually
engaged in battles with Genoa, Lucca, and Florence. This allowed time for the underlying
soil to settle. Otherwise, the tower would almost certainly have toppled. In 1198 clocks
were temporarily installed on the third floor of the unfinished construction.
In 1272 construction resumed under Giovanni di Simone, architect of the Camposanto. In
an effort to compensate for the tilt, the engineers built upper floors with one side
taller than the other. 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.
The seventh floor was completed in 1319. It was built by Tommaso di Andrea Pisano, who
succeeded in harmonizing the Gothic elements of the bell-chamber with the Romanesque style
of the tower. There are seven bells, one for each note of the musical major scale. The
largest one was installed in 1655. The bell-chamber was finally added in 1372.
After a phase of structural strengthening, the tower is currently undergoing gradual
surface restoration, in order to repair visible damage, mostly corrosion and blackening. These
are particularly pronounced due to the tower's age and its exposure to wind and rain.
Timeline On January 5, 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. The sum was then used toward the purchase
of a few stones which still form the base of the bell tower.
On August 9, 1173, the foundations of the Tower were laid.
Nearly four centuries later Giorgio Vasari wrote: "Guglielmo, according to what is being
said, in [this] year 1174 with Bonanno as sculptor, laid the foundations of the bell
tower of the cathedral in Pisa." Giorgio Vasari indicates that Tommaso di Andrea
Pisano was the designer of the belfry between 1360 and 1370.
On December 27, 1233, the worker Benenato, son of Gerardo Bottici, oversaw the continuation
of the construction of the bell tower. On February 23, 1260, Guido Speziale, son
of Giovanni, a worker on the cathedral Santa Maria Maggiore, was elected to oversee the
building of the Tower. On April 12, 1264, the master builder Giovanni
di Simone and 23 workers went to the mountains close to Pisa to cut marble. The cut stones
were given to Rainaldo Speziale, worker of St. Francesco.
Builders One possible builder is Gerardo di Gerardo.
His name appears as a witness to the above legacy of Berta di Bernardo as "Master Gerardo",
and as a worker whose name was Gerardo. A more probable builder is Diotisalvi, because
of the construction period and the structure's affinities with other buildings in Pisa, but
he usually signed his works, and there is no signature by him in the bell tower.
Giovanni di Simone was heavily involved in the completion of the tower, under the direction
of Giovanni Pisano, who at the time was master builder of the Opera di Santa Maria Maggiore.
He could be the same Giovanni Pisano who completed the belfry tower.
History following construction Galileo Galilei 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. However, this is considered an apocryphal tale, its only
source being Galileo's secretary. During World War II, the Allies discovered
that the Germans were using the tower as an observation post. A U.S. Army sergeant sent
to confirm the presence of German troops in the tower was impressed by the beauty of the
cathedral and its campanile, and thus refrained from ordering an artillery strike, sparing
it from destruction.
On February 27, 1964, the government of Italy requested aid in preventing the tower from
toppling. It was, however, considered important to retain the current tilt, due to the role
that this element played in promoting the tourism industry of Pisa.
A multinational task force of engineers, mathematicians, and historians gathered on the Azores islands
to discuss stabilisation methods. It was found that the tilt was increasing in combination
with the softer foundations on the lower side. Many methods were proposed to stabilise the
tower, including the addition of 800 tonnes of lead counterweights to the raised end of
the base. In 1987 the tower was declared as part of
the Piazza del Duomo UNESCO World Heritage Site along with the neighbouring cathedral,
baptistery and cemetery. On January 7, 1990, after over two decades
of stabilisation studies, and spurred by the abrupt collapse of the Civic Tower of Pavia
in 1989, the tower was closed to the public. 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 metres of soil from underneath the raised end. The tower was straightened
by 45 centimetres, returning to its 1838 position. After a decade of corrective reconstruction
and stabilization efforts, the tower was reopened to the public on December 15, 2001, and was
declared stable for at least another 300 years. In May 2008, after the removal of another
70 metric tons of ground, engineers announced that the Tower had been stabilized such that
it had stopped moving for the first time in its history. They stated it would be stable
for at least 200 years. Alternative candidates
Two German churches have challenged the tower's status as the world's most lop-sided building:
the 15th-century square Leaning Tower of Suurhusen and the 14th-century bell tower in the town
of Bad Frankenhausen. Guinness World Records measured the Pisa and Suurhusen towers, finding
the former's tilt to be 3.97 degrees. In June 2010, Guinness World Records certified the
Capital Gate building in Abu Dhabi, UAE as the "World's Furthest Leaning Man-made Tower".
The Capital Gate tower has an 18-degree slope, almost five times more than the Pisa Tower;
however the Capital Gate tower has been deliberately engineered to slant. The Leaning Tower of
Wanaka in New Zealand, also deliberately built, leans at 53 degrees to the ground.
Technical information
Elevation of Piazza del Duomo: about 2 metres Height from the ground floor: 55.863 metres,
8 stories Height from the foundation floor: 58.36 m
Outer diameter of base: 15.484 metres Inner diameter of base: 7.368 metres
Angle of slant: 3.97 degrees or 3.9 metres from the vertical
Weight: 14,700 metric tons Thickness of walls at the base: 2.44 metres
Total number of bells: 7, tuned to musical scale, clockwise
1st bell: L'Assunta, cast in 1654 by Giovanni Pietro Orlandi, weight 3,620 kg
2nd bell: Il Crocifisso, cast in 1572 by Vincenzo Possenti, weight 2,462 kg
3rd bell: San Ranieri, cast in 1719–1721 by Giovanni Andrea Moreni, weight 1,448 kg
4th bell: La Terza, cast in 1473, weight 300 kg 5th bell: La Pasquereccia or La Giustizia,
cast in 1262 by Lotteringo, weight 1,014 kg 6th bell: Il Vespruccio, cast in the 14th
century and again in 1501 by Nicola di Jacopo, weight 1,000 kg
7th bell: Dal Pozzo, cast in 1606 and again in 2004, weight 652 kg
Number of steps to the top: 296 About the 5th bell: The name Pasquareccia
comes from Easter, because it used to ring on Easter day. However, this bell is older
than the bell-chamber itself, and comes from the tower Vergata in Palazzo Pretorio in Pisa,
where it was called La Giustizia. The bell was tolled to announce executions of criminals
and traitors, including Count Ugolino in 1289. A new bell was installed in the bell tower
at the end of the 18th century to replace the broken Pasquareccia.
Gallery
See also List of leaning towers
Round tower, for other types of round towers Leaning Tower of Niles, a replica of the Tower
of Pisa Torre delle Milizie, a tilting medieval tower
in Rome Machang, Kelantan — home to another leaning
tower Leaning Temple of Huma — Only leaning temple
in the World The Greyfriars Tower — the remains of a
Franciscan monastery in King's Lynn. It is also leaning and is consequently nicknamed
"The Leaning Tower of Lynn" in reference to the Leaning Tower of Pisa.
Tour de Pise, a rock dome in Antarctica, was named after this tower
References
External links Opera della Primaziale Pisana — official
site Piazza dei Miracoli digital media archive,
data from a University of Ferrara/CyArk research partnership, includes 3D scan data from Leaning
Tower. Leaning Tower of Pisa at Structurae