correct documentation for where images are stored on filesystem.

docs/sources/concepts/buildingblocks.rst

@@ -12,7 +12,7 @@ Images
 ------
 An original container image. These are stored on disk and are comparable with what you normally expect from a stopped virtual machine image. Images are stored (and retrieved from) repository
 
-Images are stored on your local file system under /var/lib/docker/images
+Images are stored on your local file system under /var/lib/docker/graph
 
 
 .. _containers: