Officials have announced plans to repair one of two 12th-century towers in the Italian city of Bologna after the area around it had to secured last month over fears its leaning could lead to collapse. The city said the €4.3m (£3.7m) project to shore up the Garisenda tower – one of the Two Towers that look out over central Bologna, providing inspiration over the centuries to painters and poets and a lookout spot during conflicts – would proceed in January and February. Italy’s civil protection agency has maintained a yellow alert on the site, denoting caution but not imminent danger. The Garisenda, the shorter of two towers built between 1109 and 1119, stands at 48 metres (157ft) in height to the Asinelli tower’s 97 metres (320ft). The city’s mayor, Matteo Lepore, noted in a debate earlier this month that the Garisenda tower had leaned since it was built “and has been a concern ever since”. It sustained additional damage in the medieval era when ironwork and bakery ovens were built inside. “We inherited a situation that over the centuries has caused this illness,” he said. The mayor has asked the government to petition to make the towers Unesco world heritage sites. Work to reinforce both towers has been ongoing since the 1990s. Preliminary work on the Garisenda tower will include creating a containment area to prevent any damage to nearby structures or harm to passersby from a “possible collapse”, the city said in a statement. Video cameras will maintain surveillance of the site. The Garisenda slants at 4 degrees, compared with 3.9 degrees for Italy’s more famous Leaning Tower of Pisa. The Garisenda and Asinelli towers are named after the rival families who built them, believed to have been a way to compete over their power and wealth, and are located at what was the entrance to the city. The Garisenda was originally 60 metres’ tall but had to be lowered after it began to lean. The tower is cited several times in Dante Alighieri’s Divine Comedy and Le Rime, and Charles Dickens wrote about it in his Pictures from Italy. The Garisenda was also referred to in Goethe’s Italian Journey.