Graffiti Archaeology is amazing. We are all interested in space, place and time these days. My own interests are also focused on graffiti at the moment.
Put these things together and then find Cassidy Curtis' Graffiti Archaeology - a project developed to map graffiti-covered walls as they change over time.
The site creates a collage of photos taken of the same place by multiple photographers. It creates a visual time line of each site.
It's pretty wonderful.