We walked the "Historic Railroad Hiking Trail" shown on the satellite view. There is a nice parking lot at the trailhead near Boulder City. I highly recommend that walk. The trail takes you through several old RR tunnels and ends at the top of the dam visitor center parking structure. From there you just walk down the steps and you're on the dam. At your leisure, you can walk across, take pictures, do the Clark Griswold tourist thing, etc. Be sure to grab a soft serve ice cream from the small snack shop at the entrance to the parking garage for a shot of energy before heading back up to the trail for your return hike. Round trip, as I recall, was about 8 miles or so. There are strategically placed benches along the way if you woos out and need a rest