Something unique about Bologna are the Porticoes. It is about 40 kilometers long and dates back from 1100 and most are is still in use. Although some cities in Europe has same features but it is not as extensive as that of Bologna. It is nominated to be a UNESCO World Heritage Site. You will appreciate the shade that these porticoes will give you while walking around Bologna on hot summer days. Don’t forget to look up and appriciate some ancient old wooden ceilings that are still preserved.
To read more about the Porticoes of Bologna check this link and perhaps use the website to plan your trip to Bologna: https://www.bolognawelcome.com/en/home/discover/itineraries/culture/the-porticoes-of-bologna/