Portico of San Luca
Visitors to Bologna can't help strolling under the portici, the arcades that line so many of its streets. They are a welcome relief from the summer sun and shelter from the rain, as well as providing extra space to shops, which often display goods under them.
They began in the 11th century as overhanging upper stories of buildings in the growing city center, adding more living and storage space over the shops and businesses on the street level. As they became larger, they needed support beams and posts, and gradually the arcades grew.
In the 13th century, new arcades were required to be tall enough for a rider to pass through on horseback, a rule that led to the elegant arched arcades we see today.