The itinerary is currently not viable
Etruscans and Celts managed to see it, Romans built over it. Today, the people of Bologna only know its name and they studied it at school, but very few of them did see it. The Torrente Aposa is the only natural stream of water of the old Etruscan capital and its story is enshrined underground, beyond the houses, as a result of the gradual burial process that had started at the end of the 15th century.
Before, the Torrente Aposa had marked the industrial and economic wealth of the city, together with the rivers Savena (1176) and Reno (1191), affecting the textile industry and becoming part and parcel of the city life. From the 16th century though, because of public health issues and in order to gain new building spaces, the channels and the river itself started to be covered by bridges and artificial coverings, until completely disappearing at the beginning of the 20th century.
Everyone knows that history is a repeating cycle though, and in fact, after all the efforts to cover the stream and to make its local geographical memory disappear, between 1997 and 2000 the reclaim works recovered the ancient course of the river, but the river itself was permanently bond to the underground city by the time. Today there are two entrances, one in Piazza Minghetti and another in Piazza San Martino; they lead to the underground river for an extremely fascinating and suggestive guided tour through the foundations of Bologna (visits are not allowed at the time).
Different styles and building techniques meet along the trail, as well as remains of the different historical periods the city witnessed. There are some ruins of the ancient walls dating back to the 4th century a.D., remains of a medieval washtub and, right at the same height of the Two Towers, but 8 m deeper, tracks of a Roman bridge intrados are still visible right in that point: they allowed the Via Emilia to run over the Torrente Aposa and to continue so its track outside the city.