Tenglong Cave is a cave located 6.8 km (4.2 mi) from Lichuan City, Hubei, China. It is believed to be the longest monomer karst cave system in the world. The cave entrance is 74 m (243 ft) and 64 m (210 ft) wide, leading to 59.8 km (37.2 mi) of passageways. An underground network of streams runs for 16.8 km (10.4 mi) whilst the cave is the source of the Qingjiang River. Year round temperatures underground remain in the 16–18 degrees Celsius range.
