This is the "callejon de besos" or the "alley of kisses". This picture was actually taken the last time we were in Guanajuato; the alley was too crowded for a picture this last weekend.
I think I wrote the story before, but just in case, here it is again:

Guanajuato was an old mining town. Spanish men owned silver mines and local natives worked the mines like slaves. One of the Spanish owners had a daughter, who was very beautiful. She fell in love with a miner (or a miner's son, depending on the version of the legend). When her dad found out, he was furious - it would be like a southern debutante falling for a cotton-picking illiterate black slave. He moved her from their beautiful house near the mine to a small apartment in the city of Guanajuato nearby. When the poor miner discovered this, he was crestfallen. But, he quickly discovered where she was staying and managed to rent the apartment directly across the alley from her place. Their balconies practically touched, the alley was so narrow.


The rich spanish daughter had chaperones and she was not allowed to leave the apartment unescorted. But, she could be alone on the second-story balcony. So, the rich girl and the poor boy secretly met on their balconies and exchanged kisses there.
Well, her dad finally heard a rumor that they were meeting, and went to confront his daughter. But she refused to leave the apartment and refused to stop seeing her lover. In a fit of rage, he murdered his daughter in her room. Her poor miner boyfriend saw the entire thing from his balcony and was so distraught that he killed himself.
So today, the city of Guanajuato has a lot of visitors who come to kiss in the alley, which is supposed to be romantic or good luck, depending on your point of view.