Kinzua Bridge was one of the longest railroad bridges ever built in PA. After a tornado partially damaged the bridge (see the first photo) in 2003, they built a skywalk out of the remaining bridge and that's what I was standing on in the second picture. It scared me to death but I am so glad that I went (third photo)!  It's such a feat of civil engineering that they built this bridge that partially withstood an earthquake, did not greatly disturb the wild life in the area, and also held the weight of large trains! It's such a neat place to stop at if you are passing through PA. Make sure to gather your wits first and hope that the wind is not whipping through the valley when you come!