The two towers Garisenda and Asinelli are the traditional symbol of Bologna, strategically standing where the old Aemilian way entered the town. Today they stand right in the middle of Porta Ravegnana square, but this does not correspond to their original layout, which included wooden buildings all around their base and hanging passageways. Made in masonry work, as very few other buildings at that time, they had very important military functions (signalling and defence), beside representing with their imposing heights the social prestige of the noble families that owned them. In the late 12th century, at least one hundred towers dotted the town's skyline, but today only twenty have survived the ravages of fire, warfare and lightning. Quite recently, the statue of San Petronio made by Gabriele Brunelli in 1670, has been placed back under the towers, after being removed in 1871 for "traffic reasons".
The Asinelli Tower was built between 1109 - 19 by the Asinelli family, and in the following century it was acquired by the Municipality of Bologna. It is 97.20 metres high with a drop of 2.23 metres and an inner staircase of 498 steps completed in 1684. The plinth is surrounded by a small 'stronghold' built in 1488 to house the guards . Today, its portico hosts a few craft shops and ateliers,to recall the merchants' trade of the Medieval 'mercato di mezzo'.
The Garisenda Tower, built around the same period , is much smaller (47 metres) with a steeper drop (3.22 m) due to an early and more marked subsidence of soil and foundation. Dante, who saw the tower before the process started, compared it to a leaning Anteo in the 31st Canto of his Inferno. In mid 14th century the tower had to be lowered. The ashlar covering in selenite stone of the base dates back to the late 19th century.