World's Biggest Cave Discovered in Vietnam

The world’s largest cave passage was discovered deep within a remote Vietnamese jungle. The Son Doong cave measures 262 feet by 262 feet (80 meters by 80 meters) and at least 2.8 miles (4.5 kilometers) deep, making it the largest single cave passage ever discovered, according to National Geographic News, where the discovery was announced. The previous record holder, Deer Cave in Malaysia, is 300 feet by 300 feet (91 m by 91 m) in parts, but is only about a mile (1.6 km) long.

By contrast, explorers walked 2.8 miles (4.5 kilometers) into Son Doong, in Phong Nha-Ke Bang National Park, before being blocked by seasonal floodwaters—and they think that the passage is even longer.
In addition, for a couple of miles Son Doong reaches more than 460-by-460 feet (140-by-140 meters), said Adam Spillane, a member of the British Cave Research Association expedition that explored the massive cavern. Spillane was in the first of two groups to enter the cave. His team followed the passage as far as a 46-foot-high (14-meter-high) wall.