Tower of Pisa
The main information
• The Leaning Tower of Pisa or simply the Tower of Pisa
(La Torre di Pisa) is the campanile, or freestanding bell
tower, of the cathedral of the Italian city of Pisa. It is
situated behind the Cathedral and is the third oldest
structure in Pisa's Cathedral Square (Piazza del Duomo)
after the Cathedral and the Baptistry.
• The height of the tower is 55.86 m (183.27 ft) from the
ground on the lowest side and 56.70 m (186.02 ft) on the
highest side. The width of the walls at the base is 4.09 m
(13.42 ft) and at the top 2.48 m (8.14 ft). The tower has
296 or 294 steps; the seventh floor has two fewer steps
on the north-facing staircase.
Construction
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The Tower of Pisa was a work of art, performed in three stages over a
period of about 177 years. Construction of the first floor of the white marble
campanile began on August 9, 1173, a period of military success and
prosperity. This first floor is a blind arcade articulated by engaged columns
with classical Corinthian capitals.
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. This made the tower begin to
lean in the other direction. 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. The bell-chamber was not finally
added until 1372. 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.
After a phase (1990-2001) of structural strengthening, the tower is currently
undergoing gradual surface restoration, in order to repair visual damage,
mostly corrosion and blackening. These are particularly strong due to the
tower's age and to its particular exposure to wind and rain.
The architect
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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 (Pisa) and
the Baptistery in Pisa.
History following construction
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Galileo Galilei is said to have dropped two cannon balls of different masses
from the tower to demonstrate that their speed of descent was independent
of their mass. This is considered an apocryphal tale, its only source being
however Galileo's secretary.
During World War II, the Allies discovered that the Nazis were using it as an
observation post. A U.S. Army sergeant was briefly entrusted with the fate of
the tower and his decision not to call in an artillery strike saved the tower
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 vital role that this element played in promoting the
tourism industry of Pisa. A multinational task force of engineers,
mathematicians and historians was assigned and met on the Azores islands
to discuss stabilization methods. It was found that the tilt was increasing in
combination with the softer foundations on the lower side. Many methods
were proposed to stabilize the tower, including the addition of 800 metric
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.
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On January 7, 1990, after over
two decades of work on the
subject, the tower was closed to
the public. While the tower was
closed, 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 (50 cu yd) of soil from
underneath the raised end. The
tower was straightened by
18 inches (45 centimetres),
returning to the exact position that
it occupied in 1838. After a decade
of corrective reconstruction and
stabilization efforts, the tower was
reopened to the public on
December 15, 2001, and has
been declared stable for at least
another 300 years.