Serendipitous art: Overpainted graffiti

Graffiti and over-painted graffiti on a concrete wall looked like art to me--unintended art. This was near the entrance to the tunnel that runs from John F. Kennedy Drive behind the De Young Museum in San Francisco into the plaza area between the Academy of Sciences and the De Young. Given the proximity of the latter, I wonder if this wasn't to some extent intentional, but it appears to be random. We'll never know. In any case, it arrested my attention. 

For more serendipitous art, see my Serendipitous Art blog at serendipitousart.blogspot.com