Longgong — Dragon Palace — is a cave system 15 kilometres from Huangguoshu, near the town of Anshun. The tour runs by flat-bottomed boat through 15 kilometres of underground river, navigating chambers of stalactites and stalagmites lit from below to emphasise their scale. The largest chambers are cathedral-sized; the lowest sections require the boat to pass through passages barely taller than a standing passenger.
The boat route covers the most accessible section of a much larger system — geologists have mapped several hundred kilometres of connected passages under the Guizhou plateau in this area, fed by the same surface rivers that produce the Huangguoshu Falls. The underground river at Longgong is navigable by small boat because it flows slowly and runs at consistent depth; the guide steers by pole in the shallower sections. The formations are spectacular without requiring specialist caving — the entire tour is by boat, dry and well-lit throughout.
Longgong is separately ticketed from the Huangguoshu Scenic Area. Most visitors who come to the main falls spend a night in Anshun and combine the two on consecutive days.