Five of the 12 deepest caves on earth are in the Republic of Georgia…as of now…unless a deeper cave is discovered and verified before this question is published. Teams of international speleologists dedicated to exploring the world’s caves and cavern systems are still exploring.

As of March, 2017, Verevkina, a karst cave in Georgia, is the world’s deepest, with a documented depth of 2,204 meters (2.20 kilometers, 7,231 feet, or 1.37 miles). Karst or “solutional” caves are the most common on earth, forming in soluble rock (e.g., limestone, marble, gypsum) through geologic faults, joints, and other cracks. that, over time, is dissolved by the natural acid in groundwater.

Verevenka displaced Georgia’s Kurbera-Voronja cavern, which was the deepest known in 2014. At the time, Kurbera-Voronja had been explored to 2,197 meters, also deeper than 2 km, and the world’s cave-depth record. Sarma (3rd deepest, 1,830 m),Illuzia-Snezhnaja-Mezhonnoogo (4th, 1,753 m), and Shakta-Vjacheslav-Pantjkhina (11th, 1508 m) also are in Georgia.

France’s Gouffre Mirolda (5th 1733 m) and Jean Bernard System (7th, 1,602), Spain’s Torca del Cerro del Cueón (8th, 1589 m) and Sima de la Cornisa — Torca Magali (12th, 1,507 m), Austria’s Vogelschacht und Lamprechtsofen (6th, 1,632 m), Mexico’s Sistema Huautla (9th, 1,545, and Slovenia’s Čehi 2 (10th, 1,533) round out the world’s Deepest Dozen.

More Info: en.wikipedia.org