Popularly known as the Leaning Tower of Pisa, the Tower of Pisa is one of the most remarkable architectural structures from medieval Europe and perhaps the most recognizable buildings in the world. It is actually the freestanding bell tower or campanileof the cathedralof the Italian city of Pisa and is one of the four buildings of the cathedral complex, known as Piazza dei Miracoli. Formally known asPiazza del Duomo (Cathedral Square), the pizza is considered as sacred by the Catholic Church. It is an important centre of European medieval art and is also considered as one of the finest architectural complexes in the world. However, the Leaning Tower of Pisa, located behind thePisa Cathedral, is famous for its unintended tilt. Considered as the crowning glory of the piazza, the tower is the third oldest structure in the Cathedral Square, after the cathedral and the Pisa Baptistry.

There is a background about the construction of the Cathedral Square and the tower. In 1063, the Pisans successfully attacked the city of Palermo and plundered a great deal of treasure. To commemorate the victory and to exhibit their pomp and power, the people of Pisa decided to build a great cathedral complex, the Field of Miracles. The plan included the construction of a cathedral, a baptistery, a bell tower (the Tower of Pisa) and a cemetery.

The leaning Tower of Pisa, constructed of white marble, is 183.27 feet high from the ground on the low side, while it is 185.93 feet on the high side. The top of the tower is about 17 feet off the vertical. It was designed as a circular bell tower with 207 columns ranged around eight stories, including the chamber for the bells, adorned with 16 arches. Twin spiral staircases lined the tower’s interior, with 294 steps leading to the top. The ground story consists of 15 marble arches, while the upper six stories are equipped with 30 arches that surround the tower.

The construction of the Tower of Pisa started in August 1173, but it began to sink after the work had progressed to the second floor in 1178. This disaster was actually inevitable. The name ‘Pisa’ is originated from the Greek word for ‘marshy land’. Hence, proper pre-caution should have been taken before constructing such a heavy bell tower on the soft and unstable subsoil. In fact, thesoft soil of Pisa, composed of sand, clay, and deposits from the Tuscan rivers, and a shallow three metre foundation, were not steaty and stable enough to support the huge structure even, in the early stages of its construction. However, during that time war broke out between the Italian city-states, and the construction was halted for almost a century. This pause acted as a boon and helped the tower’s foundation to settle a bit and probably prevented its early collapse.

Construction of the tower resumed in 1272, under Giovanni di Simone and in an earnest effort to compensate for the tilt, he built the upper floors with one side taller than the other, which made the tower curved. However, the process of construction was suspended again in 1284, when in the battle of Meloria, Pisa was defeated by Genoa. The 7th floor of the tower was completed in 1319 and the bell-chamber was added in 1372. There are seven bells in the bell chamber, one for each note of the musical major scale. After that, the tower was left alone until the 19th century.

In an effort to stop the tilting, the foundations of the tower were strengthened in the 1920s, by the injecting cement grout and various types of bracing and reinforcement, but in the late 20th century the structure was still subsiding. Finally, on 27^th February, 1964, the government of Italy prayed for international help to prevent the tower from toppling. At the same time it was also considered to maintain the tilting position of the tower for added attraction of the tourists. Many alternative methods were suggested, which included the addition of 800 tons of lead counterweights to the raised end of the base. However, after more than two decades of fruitless efforts to stabilize the condition, the tower was closed to the public on January 7, 1990. Even the heavy bells were removed to relieve some weight from the top of the tower. At last, it was decided to remove 38 cubic metres of soil from underneath the raised end of the tower to prevent abrupt collapse and to slightly straighten it to a safer angle. Accordingly, after removing 70 metric tons of earth, the tower was straightened by 45 centimetres, which was equal to its position in 1838.

The Leaning Tower of Pisa was declared a World Heritage Site in 1987, along with the entire Piazza Del Duomo and the tower was reopened to the public on December 15, 2001, as it was declared stable for at least another 300 years.