The Xiaozhai Tiankeng also known as the Xiaozhai Heavenly Pit, is the world's deepest sinkhole located in the Shaanxi cluster. It is located in Fengjie County of Chongqing Municipality in China.

The Xiaozhai Tiankeng is 626 meters (2,054 feet) long, 537 meters (1,762 feet) wide, and between 511 and 662 meters (1,677 and 2,172 ft) deep, with vertical walls. Its volume is 119,349,000 m³ and the area of its opening is 274,000 m2. This material has been dissolved and carried away by the river. The sinkhole is a doubly nested structure—the upper bowl is 320 meters (1,050 feet) deep, the lower bowl is 342 meters (1,122 feet) deep, and the two bowls are on average 257 to 268 m (843 to 879 ft) across. Between both these steps is a sloping ledge, formed due to soil trapped in the limestone. In the rainy season, a waterfall can be seen at the mouth of the sinkhole.

While locals have known about the sinkholes for centuries, it was only "discovered" by the outside world in 1994, when British explorers attempted to survey its maze-like underground cave system. Despite attempting to map the underground river five times in a 10-year period, speleologists found the gushing torrent too difficult to navigate and the team never succeeded. As a result, this deep, dark underworld remains one of China's great geological mysteries.

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