The roof is in need of some restoration.  This section lacks the same paint from the rest of the roof.  Note the red color on the vertical seams.   This is not rust.  It's red paint from an earlier layer of paint showing through.

(The razor wire in the foreground sits atop a fence that separates the carousel area from a section of the children's zoo.  This is to keep people from illegally entering the zoo grounds, not the carousel.)