Editing Barcelona (section)

=== Dangerous Areas and Local Information ===
Every major city has an area more dangerous than elsewhere, and a time when this is especially true. It may even be safe during the day, but becomes sinister after nightfall. Such areas are always well-known to locals, so get advice from a hotel, tourist office, or waitress. Most guidebooks include warnings about red light or seedy areas, but conditions may have changed since the information was written.

Another point is that just because other travelers say someplace is perfectly safe, that doesn't make it true. It may only means they didn't encounter problems. I listened to an experienced backpacker swear how the dangers of a particular area were highly exaggerated or non-existent, when the previous day I had encountered three Germans who had been robbed at gunpoint there. 

Local authorities and tourist offices cannot always be relied upon, either, as they may have an interest in minimizing problems, so you always need to use your eyes, ears, instincts, and best judgment, along with a few degrees of body lean towards safety, away from recklessness.