Barcelona seems to have more than its share of graffiti. Along the railroad approaching the city, literally miles of concrete retaining walls are completely covered with paint, some of it quite arresting. That Catalunya is home to so many artists and contains so much public art may inspire the spray-can-wielding little delinquents.

Favorite canvases for taggers are garage doors and the roll-up steel doors used to protect shop windows and entrances.

Here in Ciutat Vella, our neighborhood, some shopkeepers have taken to preempting graffiti artists with graffiti of their own.

Taggers apparently respect the work of other spraycan artists. They leave doors like these alone. They'll sometimes tag the porous granite wall right next to one, but they won't spray the door itself. The key seems to be that the work must be done by artists whose vision and methods are the same as used in graffiti.

They certainly look better than gang tags, even if they aren't exactly what you might have in mind for a 1000-year-old neighborhood. And when the doors are rolled up or swung open, you don't see the designs anymore. A clever solution to an intractable problem.

Posing in front of a door thoughtlessly left blank by its owner, here is an intrepid blogger in full field gear...

... wondering how pickpockets so readily single him out.