Love the hiking you can do here. The railroad tunnel trail will give you spectacular views of Lake Mead, as well as some history lessons (if you stop and read all the signs). You can even walk past "the boneyard", which is a fenced off area where they keep old parts from the dam itself. You can either walk up on the bridge, or down below by the bridge. I didn't do the tour inside the actual dam, but maybe next time.