It's one of those places you kind of pass by and think "one of these times I'm going to see whats in there".
I pass by it on my way to Lake Mead and to Arizona and never had stopped until now. Very interesting, educational, informative and have some great views of Lake Mead, the Railroad Tunnels.
The staff is very helpful and informative about what to see or do in the area. They have free wifi and water refill station as well. Plenty of parking.