What a great trail! There is a lot to see and do around the Hoover Dam and Lake Mead area, but this trail is a great way to get in some physical activity while taking in the sights of both. The trail head is easy to find with bathrooms and a decently-sized parking lot. This is before the pay station, so there's no fee.
The trail is clearly marked and will take you through the rail road tunnels used for trucking in equipment and supplies for Hoover Dam, all the way to the Dam structure- you can turn around at any point or go all the way to the Dam itself or to the bridge and walk across (also no fee). The trail is peppered with informative plaques to get a mini history lesson along the way, and the path itself is flat, making it appropriate for all ages and abilities. The views along the way are stunning and the sheer magnitude of how impressive this structure is cannot be appreciated with a drive-through visit.
Note that dogs and bikes are permitted on this trail but not on the Dam.