Dante Alighieri was so spellbound that he wrote about it twice: in the "Divine Comedy," and in another sonnet. Charles Dickens was struck by it when traveling around Italy. And now the medieval Garisenda "leaning" tower in Bologna is sparking very modern publicity, with concern that it might be subsiding.

Streets around the Garisenda -- one of Bologna's "twin towers" perched together in the city center -- have been sealed off as scientists monitor the monument for evidence of the structure cracking and moving.

The 48-meter (158 feet) tower was built in the 12th century when Bologna was a mini Manhattan, with dozens of towers reaching towards the sky, each built by local families trying to construct theirs higher than the last. But it leans at an angle of four degrees -- only a little more upright than the Leaning Tower of Pisa, set at a tipsy five-degree angle. It was already leaning by the early 14th century when Dante wrote "Inferno," in which he described the dizzy rush of looking up at the Garisenda's leaning side. A plaque on the tower today commemorates the verse dedicated to it.

Shortened in later years, it sits in the city center beside the Asinelli -- a tower twice the height, which tourists can climb.

City mayor Matteo Lepore blocked off the area around the towers at the weekend after meeting with the city's heritage superintendent and the committee of scientists which has been monitoring the pair since 2018, to "conduct further monitoring and install sensors... to have definitive information about the state of health of the Garisenda," he announced at a city council meeting on Monday, in a speech shared with CNN.

Acoustic sensors have been placed around the tower to monitor any stress noise of cracks or creaks, while a pendulum has also been installed to track movement.

Visitor access to the Asinelli has also been halted, and a pendulum will also be installed in the higher tower.

Turning the area into a pedestrian zone is less about immediate safety concerns, and more about allowing the instruments to gather more precise data, said the mayor.

The tests will continue for the rest of the week, in order to see if the tower is doing anything other than "oscillating... as it has done more or less since it was built," said Lepore, adding that all towers and skyscrapers move up to a certain threshold.

Lepore said that the tower "has been leaning for several centuries, and it has been the subject of various interventions over decades."

A biannual report, due to be submitted at the end of November, will be brought forward, he said. The council has already lined up a company to do any work that needs doing -- one which worked on Genoa's collapsed Morandi Bridge. A council-led committee for the restoration project will also be formed.

The roads will be blocked until Friday, although according to local media, buses might never be allowed to circulate around the towers again.

Calling it the "symbol of our city along with the Asinelli tower," and guaranteeing to "protect the Garisenda as a monument," Lepore told the council, "We're working to do everything that needs to be done."

The works come after Lucia Borgonzoni, an undersecretary for Italy's ministry of culture representing the right-wing Northern League, set alarm bells ringing about the tower's safety. Borgonzoni, a politician from Emilia-Romagna, the region of which Bologna is capital, previously ran failed bids to become mayor of the city in 2016 and president of the region in 2019. Lepore represents the center-left Democratic Party, and his council opposition has cast him as failing to protect the tower.

Borgonzoni told local paper "Il Resto del Carlino" on Sunday that she was "concerned" about the oscillations recorded so far, and suggested that the scientific committee that has been monitoring it for five years had "underestimated the situation."

Lepore said on Monday that he would "abstain from the political debate, not because I don't want to participate... but because I believe that when there are important decisions to be made, including doing the right thing from an institutional point of view, it should be done calmly and with a clear conscience."

Italy's ministry for culture did not respond to a request for comment.

In the meantime, locals are continuing as normal.

"We are not afraid at all," said Fabio Bergonzini, a tour guide in the city.

"We [the Bolognesi] have never felt it to be a problem.

"Safety is always important, and obviously they need to investigate, but I don't really believe the tower is going to fall down."