These photos show some of the inner workings of the Devil's Gate Dam at Hahamongna Watershed Park in Pasadena, California. I don't know what they are, I just thought they looked interesting. These photos are overflow from a post at Pasadena Daily Photo.
Below is a broader view of the dam. To give you an idea of scale, click on the photo and enlarge it. You can see streetlights on top of the dam. The greenery is full-sized trees.
I took the photos above by shoving my camera inside the workings of the vertical grate at the bottom center of the dam.