World's Best Caves: Sarawak Chamber
Malaysians claim that the Sarawak Chamber is Earth's largest underground pocket of air. The chamber is one room, so to speak, of a track of tunnels known as Gua Nasib Bagus, or "Good Luck Cave." Think of it as nature's version of the atrium-ceilinged living room in a sprawling modern McMansion.
The cave is located in Gunung Mulu National Park in the Malaysian state of Sarawak on the island of Borneo. It remained undiscovered (by Westerners at least) until 1981. Three Englishmen, while exploring the underground network, found the cavern. According to Wikipedia:
Although they did not know it yet, the three explorers had walked into the largest known enclosed space in the world, which they later named the Sarawak Chamber. It was three times the size of the Big Room in Carlsbad Caverns National Park, New Mexico, previously thought to be the largest underground chamber. The Sarawak Chamber measured 700m (2,300 feet) long, 400m (1,300 feet) wide and at least 70m (230 feet) high. The chamber is so massive it could hold 10 jumbo jets nose-to-tail in it. The chamber is now firmly situated in the record books.