Post your guesses in the comments section below.
Guess correctly and be crowned "San Lorenzo know-it-all" for the week.
Congratulations to Larry Kinslow for being the first to correctly guess . The building is home of Insta-Smog at 254 Sycamore St. A special thank you to Keith Barros who submitted the photo to us.
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Have your own photos around town that you'd like featured in Castro Valley Patch's photo challenge? Send them to analisa.harangozo@patch.com and see if you can stump our readers!
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