The Leaning Tower of Pisa ( it, torre pendente di Pisa), or simply, the Tower of Pisa (''torre di Pisa'' ), is the '' campanile'', or freestanding bell tower, of

Pisa Cathedral Pisa Cathedral ( it, Cattedrale Metropolitana Primaziale di Santa Maria Assunta; Duomo di Pisa) is a medieval Roman Catholic cathedral dedicated to the Assumption of the Virgin Mary, in the Piazza dei Miracoli in Pisa, Italy, the oldest of the t ...

. It is known for its nearly four-degree lean, the result of an unstable

foundation Foundation may refer to: * Foundation (nonprofit), a type of charitable organization ** Foundation (United States law), a type of charitable organization in the U.S. ** Private foundation, a charitable organization that, while serving a good cause ...

. The tower is one of three structures in the Pisa's Cathedral Square ('' Piazza del Duomo''), which includes the cathedral and Pisa Baptistry. The height of the tower is from the ground on the low side and on the high side. The width of the walls at the base is . Its weight is estimated at . The tower has 296 or 294 steps; the seventh floor has two fewer steps on the north-facing staircase. The tower began to lean during construction in the 12th century, due to soft ground which could not properly support the structure's weight. It worsened through the completion of construction in the 14th century. By 1990, the tilt had reached 5.5 degrees. The structure was stabilized by remedial work between 1993 and 2001, which reduced the tilt to 3.97 degrees.

Architect

There has been controversy surrounding the 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, known for his

bronze casting Lost-wax casting (also called "investment casting", "precision casting", or ''cire perdue'' which has been adopted into English from the French, ) is the process by which a duplicate metal sculpture (often silver, gold, brass, or bronze) ...

, particularly in the Pisa Duomo. Pisano left Pisa in 1185 for Monreale, Sicily, only to come back and die in his home town. A piece of cast bearing 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. 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 In Christian architecture the baptistery or baptistry (Old French ''baptisterie''; Latin ''baptisterium''; Greek , 'bathing-place, baptistery', from , baptízein, 'to baptize') is the separate centrally planned structure surrounding the baptismal ...

, both in Pisa. File:Leaning tower of Pisa - capital of column at the top.jpg, Column capital details on top level File:Torre di pisa, capitello con scimmiette.JPG, Column details File:Pisa. Torre 02.JPG, Base wall columns File:Pisa, torre pendente (18).jpg, Flower pendant File:Pisa. Torre 01.JPG, Entrance File:Animals and monsters on the wall of the leaning tower of Pisa.jpg, Wall relief details of animals File:Torre di Pisa - panoramio (18).jpg, Outer floor tiles File:Leaning tower bell assunta.JPG, ''Assunta'' bell File:Pisa Leaning Tower bell San Ranieri.jpg, ''Pasquareccia'' bell File:Cos de campanes de la torre de Pisa.JPG, Top-level bells

Construction

Construction of the tower occurred in three stages over 199 years. 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 . The sum was then used toward the purchase of a few stones which still form the base of the bell tower. On 9 August 1173, the foundations of the tower were laid. Work on the ground floor of the white marble campanile began on 14 August of the same year during a period of military success and prosperity. This ground floor is a

blind arcade A blind arcade or blank arcade is an arcade (a series of arches) that has no actual openings and that is applied to the surface of a wall as a decorative element: i.e., the arches are not windows or openings but are part of the masonry face. It is ...

articulated by engaged columns with classical

Corinthian capitals The Corinthian order (Greek: Κορινθιακός ρυθμός, Latin: ''Ordo Corinthius'') is the last developed of the three principal classical orders of Ancient Greek architecture and Roman architecture. The other two are the Doric order w ...

. Nearly four centuries later

Giorgio Vasari Giorgio Vasari (, also , ; 30 July 1511 – 27 June 1574) was an Italian Renaissance Master, who worked as a painter, architect, engineer, writer, and historian, who is best known for his work '' The Lives of the Most Excellent Painters, Sculp ...

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 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, as the

Republic of Pisa The Republic of Pisa ( it, Repubblica di Pisa) was an independent state centered on the Tuscan city of Pisa, which existed from the 11th to the 15th century. It rose to become an economic powerhouse, a commercial center whose merchants dominated ...

was almost continually engaged in battles with

Genoa Genoa ( ; it, Genova ; lij, Zêna ). is the capital of the Italian region of Liguria and the sixth-largest city in Italy. In 2015, 594,733 people lived within the city's administrative limits. As of the 2011 Italian census, the Province of ...

Lucca Lucca ( , ) is a city and ''comune'' in Tuscany, Central Italy, on the Serchio River, in a fertile plain near the Ligurian Sea. The city has a population of about 89,000, while its province has a population of 383,957. Lucca is known as one ...

, and

Florence Florence ( ; it, Firenze ) is a city in Central Italy and the capital city of the Tuscany Regions of Italy, region. It is the most populated city in Tuscany, with 383,083 inhabitants in 2016, and over 1,520,000 in its metropolitan area.Bilan ...

. This allowed time for the underlying soil to settle. Otherwise, the tower would almost certainly have toppled. On 27 December 1233, the worker Benenato, son of Gerardo Bottici, oversaw the continuation of the tower's construction. On 23 February 1260, Guido Speziale, son of

Giovanni Pisano Giovanni Pisano (c. 1250 – c. 1315) was an Italian sculptor, painter and architect, who worked in the cities of Pisa, Siena and Pistoia. He is best known for his sculpture which shows the influence of both the French Gothic and the Ancient ...

, was elected to oversee the building of the tower. On 12 April 1264, the master builder

Giovanni di Simone Giovanni may refer to: * Giovanni (name), an Italian male given name and surname * Giovanni (meteorology), a Web interface for users to analyze NASA's gridded data * ''Don Giovanni'', a 1787 opera by Wolfgang Amadeus Mozart, based on the legend of ...

, architect of the

Camposanto Camposanto ( Modenese: ; Mirandolese: ) is a ''comune'' (municipality) in the Province of Modena in the Italian region Emilia-Romagna, located about northwest of Bologna and about northeast of Modena on the Panaro river. Although the name in ...

, 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. In 1272, construction resumed under Di Simone. 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 curved. Construction was halted again in 1284 when the Pisans were defeated by the Genoese in the

Battle of Meloria The Battle of Meloria was fought near the islet of Meloria in the Ligurian Sea on 5 and 6 August 1284 between the fleets of the Republics of Genoa and Pisa as part of the Genoese-Pisan War. The victory of Genoa and the destruction of the Pisan ...

. The seventh floor was completed in 1319. The bell-chamber was finally added in 1372. It was built by Tommaso di Andrea Pisano, who succeeded in harmonizing the

Gothic Gothic or Gothics may refer to: People and languages *Goths or Gothic people, the ethnonym of a group of East Germanic tribes **Gothic language, an extinct East Germanic language spoken by the Goths **Crimean Gothic, the Gothic language spoken b ...

elements of the belfry with the Romanesque style of the tower. There are seven bells, one for each note of the musical

major scale The major scale (or Ionian mode) is one of the most commonly used musical scales, especially in Western music. It is one of the diatonic scales. Like many musical scales, it is made up of seven notes: the eighth duplicates the first at double ...

. The largest one was installed in 1655. Italy - Pisa - Cathedral Square

History following construction

Between 1589 and 1592,

Galileo Galilei Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642) was an Italian astronomer, physicist and engineer, sometimes described as a polymath. Commonly referred to as Galileo, his name was pronounced (, ). He wa ...

, who lived in Pisa at the time, is said to have dropped two cannonballs of different

mass Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different eleme ...

es from the tower to demonstrate that their speed of descent was independent of their mass, in keeping with the law of free fall. The primary source for this is the biography ''Racconto istorico della vita di Galileo Galilei (Historical Account of the Life of Galileo Galilei)'', written by Galileo's pupil and secretary

Vincenzo Viviani Vincenzo Viviani (April 5, 1622 – September 22, 1703) was an Italian mathematician and scientist. He was a pupil of Torricelli and a disciple of Galileo.World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...

, the Allies suspected that the Germans were using the tower as an observation post. Leon Weckstein, a

U.S. Army The United States Army (USA) is the land service branch of the United States Armed Forces. It is one of the eight U.S. uniformed services, and is designated as the Army of the United States in the U.S. Constitution.Article II, section 2, cl ...

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 Artillery is a class of heavy military ranged weapons that launch munitions far beyond the range and power of infantry firearms. Early artillery development focused on the ability to breach defensive walls and fortifications during siege ...

strike, sparing it from destruction.Shrady, Nicholas (2003): ''Tilt: a skewed history of the Tower of Pisa'' Numerous efforts have been made to restore the tower to a vertical orientation or at least keep it from falling over. Most of these efforts failed; some worsened the tilt. On 27 February 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. Starting in 1993, 870 tonnes of lead counterweights were added, which straightened the tower slightly. The tower and the neighbouring

cathedral A cathedral is a church that contains the '' cathedra'' () of a bishop, thus serving as the central church of a diocese, conference, or episcopate. Churches with the function of "cathedral" are usually specific to those Christian denominatio ...

baptistery In Christian architecture the baptistery or baptistry (Old French ''baptisterie''; Latin ''baptisterium''; Greek , 'bathing-place, baptistery', from , baptízein, 'to baptize') is the separate centrally planned structure surrounding the baptismal ...

, and cemetery are included in the Piazza del Duomo

UNESCO World Heritage Site A World Heritage Site is a landmark or area with legal protection by an international convention administered by the United Nations Educational, Scientific and Cultural Organization (UNESCO). World Heritage Sites are designated by UNESCO for ...

, which was declared in 1987. 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. 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 a potential fall of the tower were vacated for safety. The selected method for preventing the collapse of the tower was to slightly reduce its tilt to a safer angle by removing of soil from underneath the raised end. The tower's tilt was reduced by , returning to its 1838 position. After a decade of corrective reconstruction and stabilization efforts, the tower was reopened to the public on 15 December 2001, and was declared stable for at least another 300 years. In total, of soil were removed. After a phase (1990–2001) of structural strengthening, the tower has been undergoing gradual surface restoration 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. In May 2008, engineers announced that the tower had been stabilized such that it had stopped moving for the first time in its history. They stated that it would be stable for at least 200 years. File:Leaning_Tower_of_Pisa_in_the_1890s.jpg, Leaning Tower of Pisa in the 1890s File:Plaque galileo.jpg, Plaque in memory of

's experiments File:Pisa schiefer turm gewichte 1998 01.jpg, Temporary lead counterweights, 1998 File:Pisa Cathedral & Leaning Tower of Pisa.jpg, The

(in the foreground), the

Cathedral A cathedral is a church that contains the '' cathedra'' () of a bishop, thus serving as the central church of a diocese, conference, or episcopate. Churches with the function of "cathedral" are usually specific to those Christian denominatio ...

(in the middleground), and the Leaning Tower of Pisa (in the background)

Earthquake survival

At least four strong

earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, fr ...

s have hit the region since 1280, but the apparently vulnerable tower survived. The reason was not understood until a research group of 16 engineers investigated. The researchers concluded that the tower was able to withstand the tremors because of dynamic soil-structure interaction (DSSI): the height and stiffness of the tower, together with the softness of the foundation soil, influences the vibrational characteristics of the structure in such a way that the tower does not

resonate Resonance describes the phenomenon of increased amplitude that occurs when the frequency of an applied periodic force (or a Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an oscillat ...

with earthquake ground motion. The same soft soil that caused the leaning and brought the tower to the verge of collapse helped it survive.

Technical information

* Elevation of Piazza del Duomo: about 2 metres (6 feet, DMS) * Height from the ground floor: , 8 stories * Height from the foundation floor: * Outer diameter of base: * Inner diameter of base: * Angle of slant: 3.97 degrees or from the verticaltan(3.97 degrees) * (55.86m + 56.70m)/2 = 3.9m * Weight: * Thickness of walls at the base: * Total number of bells: 7, tuned to

musical scale In music theory, a scale is any set of musical notes ordered by fundamental frequency or pitch. A scale ordered by increasing pitch is an ascending scale, and a scale ordered by decreasing pitch is a descending scale. Often, especially in the ...

, clockwise: ** 1st bell: L'Assunta, cast in 1654 by Giovanni Pietro Orlandi, weight ** 2nd bell: Il Crocifisso, cast in 1572 by Vincenzo Possenti, weight ** 3rd bell: San Ranieri, cast in 1719–1721 by Giovanni Andrea Moreni, weight ** 4th bell: La Terza (1st small one), cast in 1473, weight ** 5th bell: La Pasquereccia or La Giustizia, cast in 1262 by Lotteringo, weight ** 6th bell: Il Vespruccio (2nd small one), cast in the 14th century and again in 1501 by

Nicola di Jacopo Nicola may refer to: People * Nicola (name), including a list of people with the given name or, less commonly, the surname **Nicola (artist) or Nicoleta Alexandru, singer who represented Romania at the 2003 Eurovision Song Contest * Nicola people, ...

, weight ** 7th bell: Dal Pozzo, cast in 1606 and again in 2004, weight * 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 Justice). 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''. The circular shape and great height of the campanile were unusual for their time, and the crowning belfry is stylistically distinct from the rest of the construction. This belfry incorporates a correction for the inclined axis below. The siting of the campanile within the Piazza del Duomo diverges from the axial alignment of the cathedral and baptistery of the Piazza del Duomo.

''Guinness World Records''

Two German churches have challenged the tower's status as the world's most lopsided building: the 15th-century square

Leaning Tower of Suurhusen The Leaning Tower of Suurhusen (german: Schiefer Turm von Suurhusen) is a late medieval steeple in Suurhusen, a village in the East Frisian region of northwestern Germany. According to the Guinness World Records it was at one time the most tilte ...

and the 14th-century bell tower in the town of

Bad Frankenhausen Bad Frankenhausen (officially: Bad Frankenhausen/Kyffhäuser) is a spa town in the German state of Thuringia. It is located at the southern slope of the Kyffhäuser mountain range, on an artificial arm of the Wipper river, a tributary of the Uns ...

. ''

Guinness World Records ''Guinness World Records'', known from its inception in 1955 until 1999 as ''The Guinness Book of Records'' and in previous United States editions as ''The Guinness Book of World Records'', is a reference book published annually, listing world ...

'' 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 Capital Gate, also known as the Leaning Tower of Abu Dhabi, is a skyscraper in Abu Dhabi that is over tall, 35 stories high, with over of usable office space. Capital Gate is one of the tallest buildings in the city and was designed to incline 1 ...

building in Abu Dhabi,

UAE The United Arab Emirates (UAE; ar, اَلْإِمَارَات الْعَرَبِيَة الْمُتَحِدَة ), or simply the Emirates ( ar, الِْإمَارَات ), is a country in Western Asia (The Middle East). It is located at th ...

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. The Leaning Tower of Wanaka in

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

, also deliberately built, leans at 53 degrees to the ground.'Leaning and tumbling towers'
on Puzzling World website, viewed 30 July 2011

Gallery

File:Lightmatter pisa.jpg, View looking up File:Leaning tower door.JPG, Entrance door to the bell tower File:Leaning tower loggiati.jpg, External

loggia In architecture, a loggia ( , usually , ) is a covered exterior gallery or corridor, usually on an upper level, but sometimes on the ground level of a building. The outer wall is open to the elements, usually supported by a series of columns ...

File:Leaning tower staircase 6th floor.jpg, Inner staircase from sixth to seventh floor File:Leaning tower staircase 7th floor.JPG, Inner staircase from seventh to eighth (the top) floor File:Leaning tower staircase 8th floor.JPG, View from the top File:View, looking down from top of Leaning Tower of Pisa.jpg, View, looking down from the top File:The Leaning Tower of Pisa SB.jpeg, Leaning Tower of Pisa in 2013 File:Tower of Pisa - push.jpg, Tourist in a common pose at Tower of Pisa, June 2009

References

External links

* official site
Piazza dei Miracoli digital media archive
( Creative Commonslicensed photos, laser scans, panoramas), data from a

University of Ferrara The University of Ferrara ( it, Università degli Studi di Ferrara) is the main university of the city of Ferrara in the Emilia-Romagna region of northern Italy. In the years prior to the First World War the University of Ferrara, with more than 5 ...

CyArk CyArk (from "cyber archive") is a 501(c)(3) nonprofit organization located in Oakland, California, United States founded in 2003. CyArk's mission is to "digitally record, archive and share the world's most significant cultural heritage and ensure ...

research partnership, includes 3D scan data from the Leaning Tower of Pisa. * {{Authority control 1372 establishments in Europe Bell towers in Italy Buildings and structures completed in 1372 Inclined towers Round towers Romanesque architecture in Pisa Tourist attractions in Pisa Towers completed in the 14th century Towers in Pisa World Heritage Sites in Italy Christian bell towers