Locals have known of its existence for thousands of years, but Xiaozhai Tiankeng has only been explored and mapped in the last thirty years.
Called the Heavenly Pit, this sinkhole (the largest in the world) formed over the limestone Difeng cave which was carved by a powerful underground river.
Located in Fengjie, China the collapsed ceiling opening is 2,045 ft. in legnth and 1,762 ft. wide.
Over 1,200 species of flora and fauna as well as many rare animals (including the Clouded Leopard) have been found in the sinkhole. A 2,800-step staircase has been recently added to facilitate exploration.