Vietnam is home to the world’s largest known cave, Son Doong in Quang Binh Province. Discovered by a Ho Khanh in 1991, it wasn’t until 2009 when a group of British cavers repelled into the cave where they discovered a jungle, rivers and a vast array of wildlife.
Since the cave made international headlines, hundreds of tourists have booked tours of the cave at $3,000 a head.
Here are some amazing photos of the cave, some of which look like they’re from another planet.