Post your guesses in the comments section below.
Guess correctly and be crowned "Castro Valley know-it-all" for the week.
Congratulations to for correctly guesing . The American Water Landmark plaque sits near the Lake Chabot Dam overlook.
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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!
Shout out to Castro Valley Patch reader David Bushong for supplying us with this week's photo!
Find out what's happening in Castro Valleyfor free with the latest updates from Patch.
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