While reviled by public officials and city sanitation workers, graffiti art continues to grow throughout the U.S.

Graffiti Archaeology is the study of graffiti-covered walls as they change over time. The project is a timelapse collage, made of photos of San Francisco graffiti taken by many different photographers from 1998 to the present.

The site allows you to visit some of San Francisco's classic spots, see what they looked like in the past, and explore how they have changed over the years.

Currently visitors can browse through five different locations in the city. The real star of the site is the graphical interface that allows visitors to zoom in and out through the different phases of each site's respective artistic evolution. Along with this feature, visitors can look at each site during various transformations, giving one a sense of how each wall has been changed by a number of graffiti artists.