Nevada has one national park, and no it is not the Las Vegas Strip, it is Great Basin National Park located approximately mid-state. US 50, also known as The Loneliest Road, cuts through it, taking you to Reno on the west side of Nevada from the state's eastern border with Utah.
Great Basin got its name because it has no natural drainages: any rain water soaks into the soil, evaporates, or flows into the salty lakes in the area, and does not find its way to an ocean. The Great Salt Lake in Utah is an example of this kind of lake.
The Loneliest Road is just that - very lonely. It follows the old Pony Express route, and while you are driving along, just you and the scenery, you can picture what it was like for that lonely rider on horseback.
The few little towns between Utah and Reno have capitalized on this and you can get a passport that gets stamped in each town to prove you drove the length of the road.
One of the highlights of the park is Lehman Caves, which is practically in Utah, although not right on Interstate 15, it's still off the beaten track.
Periodically, they organize groups of volunteers to help clean the caves. Because there is no air movement underground, the bits of lint, hair, and whatever that fall off the visitors accumulates, and the limestone formations start to look a little dull and fuzzy. They use hardware store paint brushes to knock it to the floor, and it gets vacuumed up with shop vacs.
Of all the volunteering-to-help-nature projects I've heard of, this sounds like one of the nicest, because it is always 50 degrees in the caves - no scorching sun or wintry winds. Just stand there with a paint brush. The only drawback for me is that I'm claustrophobic and afraid of the dark, and my particular fear is of dark caverns such as crawl spaces, so I don't really see myself rushing to sign up for what they call Lint Camp. But it was a nice thought for about a minute.
P.S. I forgot to tell you that Great Basin is the third least-visited national park in our country, behind the ones in Alaska.