Hidden Marvel: Vietnam’s Son Doong Cave Reveals Its Secrets After Years Of Discovery

Interior of the Thien Cung cave / Paradise cave, one of many limestone caves in Ha Long Bay / Halong Bay / Vinh Ha Long, Quang Ninh Province, Vietnam. (MARCIA VAN DR MEER/GETTY IMAGES)

Hidden behind treacherous mountains deep in the tropical forests of a national park in Vietnam, the world’s largest cave sat untouched and sealed up for millions of years–until just recently.

A tourist looks at stalactites and stalagmites inside the Phong Nha Caves. The caves can be found near the Phong Nha Nature Reserve. The Vietnamese Government is proposing that this Nature Reserve become a World Heritage Site. The nature reserve contains a rare species of Langur. These Langur can only be found in this small region of Vietnam. (PETER CHARLESWORTH/GETTY IMAGES)