Son Doong cave(Vietnamese: Hang Son Doong) is world's largest cave, located in Quang Binh province, Vietnam. It is found by a local man named Ho Khanh in 1991 and was recently discovered in 2009 by British cavers, led by Howard Limbert. The name "Son Doong" cave means "mountain river cave", It was created 2-5 million years ago by river water eroding away the limestone underneath the mountain Where the limestone was weak, the ceiling collapsed creating huge skylights...

Source: SONDONG CAVE