Glass Observation Deck Introduction: Longwantan has built China's first high-altitude glass observation deck on the top of the cliff. The entire U-shaped observation deck extends out of the cliff and hangs in the air. Standing on the observation deck, you can see a forest sea; looking down through the glass of the plank road, the feeling of flying more than 300 meters in the air is somewhat frightening. Of course, it’s also a great place to take photos.