It's like the trick pictures on ebay--look in the reflection on the water, you can see everything!
Inquiring minds want to know--where is the source for this bridge? I'd like to hope it's still around and just misplaced....
When I clicked on the link to view in Flickr I got a message reading "This photo falls outside your current SafeSearch filter. You can click through to see it if you want." The photo is marked as "restricted." Its a false alarm apparently, since this bridge clearly has all its private parts covered in concrete. No naked bridges here.
The source on Flickr is a former IDOT worker, so I'm assuming there was a notation on the back stating it's in Ankeny. I've asked if he knows exactly where in Ankeny it was.