The Leaning Tower of Pisa is gradually straightening thanks to stabilization work on it, a study by Italian scientists found, cited by the Daily Mail and BTA.

The tower’s tilt has been a source of concern for engineers, historians and thousands of tourists for decades.

An 11-year stabilization project reduced its tilt by 38 cm by 2001, and in the twenty-one years since then, the tower has straightened another 4 cm. Although the tilt has been reduced, the tower’s body still “rocks” with an average of about 0.5 mm per year according to Nunciante Scuglia, professor of geotechnics at the University of Pisa. “Today, however, the stability of the bell tower is better than expected,” he told Italian news agency ANSA.

The bell tower, a symbol of the power of the maritime republic of Pisa in the Middle Ages, has managed to survive unscathed at least four major earthquakes that have struck the region since 1280. A 2018 study found that it was the softness of the soil beneath the foundations, which was initially responsible for its swaying, that protected it from the strong tremors. According to theories, the 57-meter tower tilted during construction, which began in 1173. The reason lies in a faulty design, the foundations of which are only three meters deep and are built on a weak and unstable soil layer.
The soil under the foundations is softer on the south side, which gave rise to the infamous slope.

The builders tried to make up for it as they built the last eight floors. They made their floors shorter on one side, making the structure curved in addition to being tilted.
Construction was not completed until 1319 due to various battles between Pisa and Genoa, Lucca and Florence, but these pauses gave time for the soil in the foundations to settle.
In 1990, the tower was still leaning 5.5 degrees to the south and was closed to the public due to fears it would collapse.

After implementing several unsuccessful strategies to straighten the structure, the engineers decided to try so-called “soil extraction”. This involved digging two truckloads of earth under the north side of the tower, then using steel cables to pull it upright. The procedure worked, but the team found that the building continued to tilt during the winter rains, as a large body of water collected under its northern side. Drains had to be dug so that the water flowed into special wells and thus keeping the foundations stable.
The project was completed in 2001 and resulted in the tower being straightened by 38 cm or 0.5 degrees. Since then, adjustments have been made, with the slope continuing to gradually decrease.