Phong Nha-Ke Bang National Park, Vietnam
Right in the heart of this Vietnamese national park is Han Son Doong, also known as the largest cave in the world. This is the place to visit if you love spelunking and alien landscapes that can house a block of New York City skyscrapers. It’s also home to the world’s largest stalagmites, measuring up to 260 feet, or 80 meters into the air. There’s a high level of biodiversity and endemic species, vital for the limestone landscapes (WHC).