It’s October in southern China, and a group of explorers are teetering on the edge of a vast sinkhole. Bravely, they descend into the darkness, with just a single rope between them and certain death. But as they near the bottom, they discover an incredible landscape hidden beneath the earth.
In recent years, a considerable number of sinkholes have made the news. Like, for example, the vast void that almost swallowed up a Florida resort in 2013. Or the chasm that destroyed a huge chunk of road in Fukuoka, Japan in 2016. But what exactly is behind the sudden appearance of these terrifying holes?