Bologna was once threaded with canals — the city used water power for its textile mills and silk works for centuries — but in the nineteenth and twentieth centuries most of them were covered over. The Canale delle Moline still flows in a narrow brick channel beneath the streets of the Quadrilatero.
The Finestrella on Via Piella is a small window cut into the wall along the pavement that lets you peer down at the water below. With its mossy walls and overhanging houses it looks startlingly like a tiny Venice. It costs nothing, takes thirty seconds, and is one of the city's signature Instagram stops.