Don't let the bars and forbidding stone fool you.
This place was designed to free your mind.
But where in Castro Valley is it?
Put your guess in the comments below.
No one guessed that last week's entry was the recycling station behind the Lucky's supermarket.
Have photos that you'd like to feature? Send them to editor email@example.com and see if you can tease the Valley.
About this column: Every week or so, we'll test your knowledge of places and things in Castro Valley. To browse puzzles from past weeks visit our archives.