Have you ever seen love padlocks?
Lovers lock a padlock onto a bridge (although I’ve also seen it on a well in Salamanca!), usually with an engraved message like the names of the couple. The padlock keys are then traditionally thrown into the water so that the love is forever ‘locked’ up.
I’ve encountered these locks in Salamanca, Krakow, Munich, Ljubljana and Budapest.
Here is a video of the Ponte Milvio in Rome: