With the upcoming Allentown Art Festival this weekend, we've been showing you some different forms of art outside the traditional spectrum. One of our favorite kinds of art is graffiti (when tastefully done).

In the past, graffiti had a major negative connotation. It was often known as ways for gangs to mark their territories or for hoodlums to write vulgar words on the sides of buildings.

Today, however, graffiti has evolved into a true art form. Cities all over the world have  this art form peppered throughout their streets. Artists paint graffiti on buildings, subway trains, buses, park benches, or just about anything else you can think of.

Beware of police if you think of trying this urban art form as it is still illegal unless there is consent of the owners of the property. Check out a few of our favorites i the gallery above.