Strangely shaped concrete blocks forming a small retaining wall next to the south portal of Caltrain tunnel #3, San Francisco.

Shot with the Nikon D70s and the 18-70mm f/3.5-4.5 zoom at 70mm, ISO 400, f/7.1, shutter 1/1250 sec. Exposure, contrast, highlights, shadows, and levels adjustments in Aperture.