Admire the 850-year-old Leaning Tower of Pisa

"The bell tower remains a solid monument to this day," said Andrea Maestrelli, president of the Opera della Primaziale Pisana (OPA), the body that oversees the cathedral complex that includes Pisa, in a statement marking the 850th anniversary of the tower's construction.

However, in the early 1990s, the tower was measured to be leaning 4.5 degrees, forcing the Italian government to find a way to stop it. The work to stabilize the tower lasted 8 years, starting in 1993.

Specifically, the tower is back to vertical and is 4 cm taller than it has been in about two decades, since efforts to maintain and stabilize the tower were launched.

The monitoring group's latest report "highlights a trend of a decrease in tilt of about 460 mm", Maestrelli added, adding that the tilt had returned to its level at the beginning of the 19th century.

In addition, experts say the future of the Leaning Tower of Pisa is "very bright" as it is equipped with a ground-based monitoring system, with satellites tracking the smallest changes of the tower. This move makes the tower one of the most closely monitored monuments in the world.

"Considering that this is an 850-year-old patient, with a tilt of about 5 meters and a subsidence of more than 3 meters, the health condition of the Leaning Tower of Pisa is excellent," said an OPA spokesperson.

The first stone of the tower was laid on August 9, 1173. It was not until the third floor that the tower began to lean to the north. One of the reasons for the leaning tower is the geographical characteristics of the city of Pisa itself, with soft soil, mainly composed of mud, sand, and clay. Construction of the tower was interrupted until 1275 and completed in the mid-14th century.

Several other buildings in Pisa also lean because they were built on soft ground, including the 12th-century church of San Nicola to the south of the leaning tower and the church of San Michele degli Scalzi to the east of the tower.

The Leaning Tower of Pisa is the name of a famous tower in the city of Pisa (Italy) which was started to be built in 1173, nearly 60 meters high. Every year the tower welcomes more than five million visitors.

The unique feature of the Leaning Tower of Pisa is that it tilted due to subsidence while it was still under construction. To stabilize the structure, engineers used a number of geotechnical measures to keep the tower in its current state.

For centuries, engineers, scientists and people have held their breath many times over the fate of the iconic bell tower.

To date, it has survived four earthquakes and swayed back and forth several times. Yet somehow, the tower still stands with a tilt that is not too far from its original position.