Abkhazia, the breakaway republic of Georgia, is home to all four of the deepest known caves in the world, including Krubera Cave, once the deepest and now second to Veryovkina Cave, which, at 1.3 miles (2,212 meters) down, holds the record. 

When it was first documented in 1968, only 377 feet of it were charted, but since then, with additional expeditions, it has grown deeper and deeper. The entrance to this vertical cave system lies between two mountains—Fortress and Umbrella—in the Arabika Massif of the Western Caucasus. This remote place is tough to access, and it took dozens of speleological expeditions and 50 years for it to finally claim the record, in 2018, when members of Moscow-based speleological clubs reached its depths. 

The round trip—top to bottom and back—takes professional speleologists about a week and is, as one might expect, incredibly risky. Two years ago, the team almost drowned in a sudden flood that happened at the bottom camp. Despite the risks, the team and scientists keep working in the cave, and they hope there may be further depths.