Barra Honda National Park, Costa Rica
Tubular soda straws and furry kinkajous—this park’s geological features and fauna evoke visions of another planet. And while the 5,600 acres of tropical dry forest are remarkable, the most impressive thing lies beneath. Terciopelo Cave is one of 42-known caverns and is best experienced during the dry season (November through April). For a small fee, you’ll get admission, gear, and a local guide.