Bridge of lovers
Tumski Bridge is one of many bridges in Wrocław but it is special, as it's known as a bridge of lovers. The nickname comes from the tradition of putting locks with lovers names or initials at the sides of the bridge, so that you're relationship would survive forever. As romantic as it is, unfortunately I need to crush your dreams, because the locks are too heavy and put too much weight on the bridge, so in order for it not to crush, the locks are being cut off once in a while (hopefully it doesn't affect the relationships ;P)
Last winter, when the whole city was beautifully decorated for Christmas, the bridge had heart-shaped lights to highlight romantic nature of this place. A bit cringe-worthy but it looked very pretty.
The bridge is located between the city center and Ostrów Tumski (beautiful place, a must-see for tourists), so you'll probably cross it at some point of the sightseeing. The area by the river is also pretty nice, you can just sit there and look at nice landscape, known from postcards. The bridge is open only for pedestrians. You won't spend more than five minutes on this bridge, as it's rather short but it's nice to know this tradition, especially that it's rather old, constructed in 1889.
In my opinion it is a must-see in an old town together with Ostrów Tumski, which is just across the bridge.