Prior to repair work between 1990 and 2001, the tower leaned at an inclination of 5.5 degrees, but it currently leans at around 3.99 degrees. The tower is still standing after all these years.
The Leaning Tower of Pisa, also known as the Giotto di Bertoldo (Giotto of Bertoldo), was built from 1276 to 1348. It was designed by Antonio da San Gallo, who also designed the famous bell tower of Venice's St. Mark's Square. The tower has three floors, with an elevation of 135 feet from its base to its top. It is made of limestone with marble decorations. When it was first built, the tower was upright with an opening in its center that allowed people to see inside. Over time, however, weather caused the tower to lean until only one side is vertical. This photo was taken in 2002 when the tower was at its maximum tilt of about 23 degrees.
One degree equals 57.3 minutes of arc. At its current angle of 3.99 degrees, this means the tower is tilting by 9.77 minutes of arc each year. The rate at which it is leaning increases the burden on its foundations. In order to prevent the tower from falling over, builders added more than 20 feet to its height in 2001.
Returning to physics, the tower now leans at 3.99 degrees. Physicists estimate that the greatest angle before the tower falls is 5.44 degrees, based on the weight and height of the structure (at its worst, the tower once leaked briefly at 5.5 degrees). A team of engineers has predicted that without further action the tower will collapse within 100 years.
The leaning of this famous monument is caused by shrinkage, or loss of volume due to damage to the outer walls. The tower was built with thin walled plaster between old and new wood, and over time the wooden frame inside the plaster wall has dried out and shrunk, causing the tower to lean.
It all started in 1178 when the first stones were laid down for what would become the world's most famous leaning building. At the time, it was known as "Il Campanile" ("the bell tower"). The builder of the tower was Bonnano Pisano, a wealthy merchant who had made his money trading with Egypt and Syria. According to some historians, it may have been designed by an Egyptian architect brought to Italy by Bonnano Pisano.
Over the next few centuries, the tower was remodeled several times. In 1363, during one of these renovations, it was discovered that the tower was leaning more than two inches from its original position. Work stopped until the problem was fixed, which it wasn't.
But because of natural forces acting on the building, such as wind and ice buildup, there are times when it leans significantly more than this.
The leaning of the tower is due to natural forces acting on a flat-topped stone structure without any supporting walls. The uneven distribution of weight and soil pressure causes the tower to tilt in one direction or another, depending on the location.
There are two main factors that determine how much the tower will lean: the type of rock from which it is built and the distance to the next large body of water. If the tower was closer to a mountain, it would tend to lean toward the mountain. If it were located near the coast, it would tend to lean away from the coast.
Closer inspection of photos taken over time shows that the base of the tower is not perfectly level; there is a slight slope of about 1 in 100. This is why engineers must account for both vertical and horizontal forces when determining whether the tower is safe for visitors. If it were not for this sloping base, the Leaning Tower would be completely vertical.
Approximately a 10 degree angle The Tower of Pisa is 60 meters tall and leans at a 10 degree inclination till 1990. Despite being meant to be exactly vertical, it began to tilt during construction. The cause is not clear but may have been due to soil instability beneath the foundation.
The tower has been called Europe's tallest building site safety hazard. Until 2010, when the dome caved in on itself, it was the world's most dangerous job. The tower continues to lean today, but at a much reduced rate of 1/16 of a degree per year.
The tower was stabilized as a result of restoration work completed between 1999 and 2001. Engineers placed weights on the structure's north end while removing earth from below, forcing it to sink back in that direction gradually. The Leaning Tower of Pisa still leans south, although at just 3.99 degrees. It is the only medieval monument to survive in its original form in Europe.
In response to questions about the future stability of the tower, officials with the city government stated that the tower is now safe for visitors to enjoy. However, they added that if economic conditions were to change for the worse, more money could be allocated toward maintenance and repairs.
The story of the tower's stabilization has been used as an example in books and articles about urban planning and architecture. A chapter is also devoted to it in the book The Leaning Tower: A History._
The first written record of the tower being out of plumb can be found in a document dated 1163. At that time, the tower was described as "our house tilted". Over the next 200 years, several attempts were made to correct the tilt, but all efforts failed miserably. In 1272, the bishop ordered the construction of a new town wall, which caused more damage than good because it cut off access to the base of the tower. After this incident, the tower was left alone until it was restored in 1516.
This medieval structure, optimistically nicknamed "the Welsh Tower of Pisa," leans at 10 degrees to the vertical, most likely due to subsidence. The southernmost tower has a tilt of more than 10 degrees due to subsidence—greater than the Tower of Pisa! This occurs because the rock upon which it is built is porous. The water that seeps into the rock lowers its temperature and causes it to contract. As this process continues over time, it creates a gap between the rock and the side of the castle facing the valley floor.
Caerphilly Castle was built in 1180 by Henry de Lacy as a protective barrier against his native Wales. The original tower was about 70 feet high with an attached keep on the south end. Over the years, the tower has been expanded with additional floors added. It now stands nearly 100 feet tall with 12 floors.
The castle today is a living museum where you can see some rooms with interactive displays that bring to life parts of Henry de Lacy's story. Other rooms are used for special events such as weddings and parties.
Caerphilly Castle has been listed as one of Britain's best-preserved castles and is said to be the largest town hall in Europe. It's a great place to visit with kids because of all the fun activities to do together.