Remains of ? (something) on the metal grating wall of a passenger shelter at Hayward Park station, San Mateo, California.

Shot with the Nikon D70s and the 18-70mm f/3.5-4.5 zoom at 44mm, ISO 400, f/11, shutter 1/320 sec. Exposure, contrast, saturation, levels and highlights adjustments in Aperture.