Built in 1931, Philadelphia's Spring Garden School is now being
converted into affordable housing.
But the building lay abandoned from the 1990s to 2016 exposed to vandals and graffiti artists.
4 Years/40 Walls offers a four-year chronology of some of their work.
4Years/40Walls is interactive. Click on a picture to see the
same wall at two or four year intervals.
The year appears below the picture on the left.
The photographs were taken in July 2011, August 2013, and December 2015.
The first 12 walls include shots from all three years.
The rest compare 2011 and 2015. -John Bendel