A British expedition team has discovered what they believe to be the world’s largest cave deep within the Vietnamese jungle, the Telegraph reports. At 650 feet high and nearly 500 feet wide, Hang Son Doong—or Mountain River Cave—is twice the size of current record holder Deer Cave in Sarawak, Malaysia. The 13-man team spent five days exploring the cave and is still plotting its exact dimensions.
"It is a truly amazing-sized cave and one of the most significant discoveries by a British caving team," said a team member. The cave’s entrance was discovered by the group’s Vietnamese guide in 1991, but locals never ventured inside due to the small size of the cave mouth and a “frightful wind and noise” it emitted—caused by a large underground river.