This Nevada trail runs from the Lake Mead Visitor center to the Hoover Dam visitor center. It follows the route of a railroad built specifically to haul supplies to the Hoover Dam construction site as it was being built. The trail has several nice overlooks to view Lake Mead and it has five tunnels. The hard pack gravel surface is an easy ride. Its short 3.7 mile length does not seem attractive to biking but the historic value along with a connection to the much longer Mountain Loop Trail can make for a very enjoyable visit. One cautionary note, this is in a desert region. I would avoid this in the summer. It can get very hot. No matter when you go be sure to bring plenty of water.
Learn more about the trail here: https://www.nps.gov/lake/planyourvisit/hikerr.htm
See a video of my ride here: https://youtu.be/W75wzXbOY8I