The underside of Interstate 280 and support columns, above the track at the north portal of Caltrain tunnel #1, San Francisco.

Shot with the Nikon D70s and the 18-70mm f/3.5-4.5 zoom at 70mm, ISO 400, f/6.3, shutter 1/250 sec. Exposure, highlights, and monochrome adjustments in Aperture.