The Piazza del Duomo in Pisa is one of the most famous sites in Europe, entirely due to an aesthetically designed tower that was poorly engineered. Thankfully there are hordes of tourists willing to prop the poor tower up with a carefully positioned hand (or hands). I visited Pisa with my brother on a blustery day in the fall of 2003. We arrived by train from Florence, and noted the wind was so strong that the Arno River was almost flowing backwards. Despite the cool weather, the Piazza dei Miracoli was rather crowded with visitors, which made it a bit of a miracle to get pictures of the tower, cathedral, and the perfectly round baptistry with only a few other tourists in the background. I had hoped to go up the tower, but it was closed; I can't remember whether it was due to the wind or to construction. My brother was a bit tired of cathedrals and museums after his first week and a half in Europe, so we wandered around the square for about an hour before heading back to Florence. The architecture of the three main buildings in the piazza was incredible, and definitely worth a visit. Maybe someday I'll return and get to climb up the tower and tour the cathedral and baptistry.

Logistics: The Piazza del Duomo is small enough that it is extremely easy to walk around; the piazza may be reached by bus or by an approximately twenty minute walk from the Pisa train station.