2. Great Basin National Park, Nevada
Great Basin is full of surprises, especially if you think Nevada is just desert and casinos. This high-altitude park has 13,000-foot peaks, alpine lakes, and one of the darkest night skies in the U.S. That means stargazing here is top-tier. During the day, you can explore ancient bristlecone pine groves and some trees are over 4,000 years old. Lehman Caves is another major highlight, with guided tours that take you through stunning marble caverns. There’s also plenty of hiking, from short scenic strolls to intense summit climbs. Unlike many parks, it rarely feels crowded. You’ll get sweeping views and peaceful trails, often all to yourself. And best of all, it’s one of the highest altitude national parks without entrance fees.