Photo taken by Bill Dunbar
BH Photo #205751
built around 1912 when the railroad relocated the line through that area making the cut to the right and filling to the left (west)
also known locally and by Story County Conservation as "Mousehole"
People usually refer to them as tunnels if they are very long. I consider a tunnel to be cut through existing geology. This is probably more formally a rigid frame concrete bridge. Still, cool to honk the horn for the kids in all of us.
I honestly don't know whether to classify it as a bridge or a tunnel.