During this time of prosperity, nearly every powerful and wealthy family built its own tower to assert its dominance to the point that the city once possessed as many as 180 towers!
The twin towers were both built between 1109 - 1119 AD, but unlike many of the city's towers, they have survived largely intact since their construction.
The higher tower belonged to the Asinelli family and rises 97 metres, a skyscraper by its own merit, while the smaller tower, la Torre Garisenda, is about half the size at 48 metres. The latter originally reached 60 metres, but was deliberately reduced in the 14th century for fear of collapse. Both towers are visibly leaning by about 2-3 metres!
La Torre degli Asinelli is open to the public, but the courageous visitor must climb some 498 steps to be rewarded by spectacular views from the top. The reward is a top view of Bologna, which you can't really miss.