Post your guesses in the comments section below.
Guess correctly and be crowned "Castro Valley know-it-all" for the week.
Congratulations to for being the first to correctly guess . The tower-like structure can be found on Alma Avenue, across the street from the
Have your own photos around town that you'd like featured in our Castro Valley photo challenge? Send them to analisa.harangozo@patch.com and see if you can stump our readers!
