Hang Son Doong, the world’s largest cave, located in Phong Nha-Kẻ Bàng National Park, Bố Trạch District, Quảng Bình Province,Vietnam. Discovered in 1991, the cave remains largely unexplored. Just recently, tourist can pay an estimated 3,000 US dollars for a tour-guided exploration of this immense world.
If you are not going there to see this fantastic world in person, watch this video which shows the immensity and sheer beauty of the cave from a drone’s perspective (some footage taken by land). It will surely leave you in awe.