ROME — Italy’s famously Leaning Tower of Pisa is a little less off-kilter.

Nearly two decades after engineers completed consolidation work to keep the tower from toppling over, officials monitoring the monument said recently that its famed tilt had been further reduced by 4 centimeters, or 1.5 inches.

The tower “is continuing to straighten,” said Nunziante Squeglia, an engineering professor at the University of Pisa and a consultant to the committee that monitors the tower.

The correction is the result of measures carried out just before the turn of this century to ensure that the tower would not collapse.

“We knew those measures would have protracted consequences,” Professor Squeglia added, but engineers could not foresee that the tower would reverse its tilt, he said.

The tower, one of Italy’s most famous monuments, is also one of its most fragile.

Built as a bell tower for Pisa’s cathedral and baptistery, it began sinking into the ground five years after construction began in 1173. The pillar took almost 200 years to build, and included various unsuccessful attempts to correct the tilt.

At some point over the centuries, its perilous slant made the tower — listed as 58.36 meters (or about 190 feet tall) — a must-see attraction for visitors to Italy.

“Locals used to think of it as an architectural failure, then it was seen as a boon for the city,” said Gianluca De Felice, general secretary of the Opera Primaziale Pisana, the nonprofit organization responsible for the monuments in Pisa’s so-called square of miracles, where the tower is located.

In January 1990, the tower was closed to visitors — around 800,000 a year — when officials became concerned about its long-term stability. It reopened 11 years later, after various methods to counteract the tilt managed to reduce it by 15.95 inches.

“We rejuvenated the tower by around 200 years,” bringing the incline to where it was around 1820, said Salvatore Settis, one of the members of the committee that oversaw the consolidation of the monument. “The good news is that the tower continues to straighten — if slightly,” he said.

Today, Professor Settis leads a committee of three in charge of monitoring the tower and reporting on its “state of health,” which is currently “very good,” he said in a telephone interview.

The tower, he added, was “the most monitored monument in the world,” with more than 100 sensors giving hourly readings on a host of elements, from the external and internal temperatures to wind velocity to microfissures in the materials to soil movement.

Officials in Pisa have also halved the number of visitors allowed to clamber to the top of the tower for a sweeping view of the Tuscan surroundings.

“The climb has to be controlled” so that visitors can tour in groups and reserve a trip in advance, said Mr. De Felice. Only about 400,000 visitors climb the tower each year, while nearly three million visit the site, which includes the cathedral, baptistery, two museums and a cemetery.

The Leaning Tower of Pisa, however, remains by far the most photographed attraction, even though the renovations cost it its status as the world’s leaning-est tower. Now, towers in Switzerland and Germany are contending for that title.

Though the Pisa tower is on a reverse path, that doesn’t mean it could ever completely straighten.

“At the current rate, the tower would take around 4000 years,” said Professor Squeglia.

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