Ravenna's answer was to create a pond in the ancient crypt! Visitors to this old church can peak under the alter to find this goldfish pond, which is apparently visited by ducks sometimes too.
Bologna has some 40km of porticos in total, since while the other Italian cities banned them, Bologna made them compulsory. A great idea of you ask me, as they provide shelter from the elements - the scorching sun in summer and the rain or snow in winter. If you stand under the oldest portico in Bologna you can find a hidden secret - the story of the three arrows.
Two of the arrows can be seen in the photo below, can you find them? Took a lot of searching and a sore neck to spot them from the ground!
An adventure loving historian with a soft spot for armour and motorbikes.