4. Biscayne National Park, Florida
If you’re into tropical vibes and water adventures, Biscayne is the perfect free-entry park for you. Located just south of Miami, this park is 95% water. That means boating, snorkeling, and kayaking are the best ways to explore. You’ll float over coral reefs, shipwrecks, and seagrass beds filled with sea turtles and colorful fish. On land, there’s a visitor center and a few trails, but the real magic is offshore. Guided tours and boat rentals do cost money, but entrance to the park itself is completely free. Elliott Key, the largest island, is great for a peaceful beach day or a night of camping under the stars. It’s one of those places where you feel far from the city, even though the skyline is just across the bay.