Sinkhole 1, known as Dinosaur Outlook, lies 3km from the entrance deep inside Son Doong Cave, the world’s largest cave. Measurements by a British-Vietnamese expedition team put its depth at an impressive 449 metres, from the lowest point of the sinkhole’s rim to the cave floor, with its widest section measuring 125 metres.
On sunny days, particularly between 11am and 1pm, sunlight streams directly into Dinosaur Outlook, creating a spectacular, almost otherworldly scene that illuminates the vast cave chamber.
At the bottom of the sinkhole stands a giant stalagmite known as the Wedding Cake. Its relatively flat surface, shaped by frequent waterfalls, and distinctive rounded form give it the appearance of a wedding cake.
About 1km from Dinosaur Outlook lies another famous sinkhole in Son Doong Cave, known as Garden of Edam, or Sinkhole 2. It is a highlight of expeditions into the world’s largest cave, formed when the cave roof collapsed after underground water eroded the limestone over millions of years.
According to surveys by the British-Vietnamese expedition team, Garden of Edam is 252 metres deep and 175 metres wide, and can be reached through only one access route.
Remarkably, a vast, lush primeval forest thrives underground within the sinkhole, creating a unique and vibrant ecosystem.
Kong Sinkhole, deep within the Tiger Cave system in Phong Nha-Ke Bang National Park, was first discovered by a cave expert in 1997. More than 20 years later, experts explored further with the help of drones, discovering a distinctive eye-shaped opening. Struck by its unusual appearance, the expedition team named it Kong Collapse, inspired by the character King Kong in the film “Kong: Skull Island”, which was filmed in Quang Binh, now part of Quang Tri Province. “Collapse” refers to the sinkhole itself.
At 450 metres deep, Kong Sinkhole has been developed for adventure tourism. Reaching it is a challenging journey that involves trekking through forest, swimming through dark caves and exploring three consecutive caverns. The most demanding part is abseiling 100 metres vertically from the eye-shaped opening to the bottom of the sinkhole.
Nightmare Sinkhole, part of the Hung Thoong cave system in Phong Nha-Ke Bang National Park, is 250 metres deep and conceals a mysterious underground river. Its name arose from arduous expeditions that pushed explorers to their physical limits and consumed considerable time.
The operator of Hung Thoong tours has now introduced a zipline experience across Nightmare Sinkhole for adventure seekers. Participants can take in the entire sinkhole from above and experience the sensation of hanging in mid-air while looking down into its immense depths.
Recently, adventure tour operator Jungle Boss, in collaboration with the US-based National Speleological Society and the management board of Phong Nha-Ke Bang National Park, announced the results of a survey of a giant, previously unexplored sinkhole in the Cha Noi-Khe Gat area of the national park.
The sinkhole resembles an inverted bowl, widening towards the bottom. Its oval-shaped opening measures 190 by 140 metres, while the interior is 250 metres long, 200 metres wide and 120 metres deep. It covers an estimated two hectares, equivalent to about three standard football pitches.
Location of Phong Nha-Ke Bang National Park in Quang Tri Province. Photo: Google Maps.
Photos: Oxalis - Jungle Boss
