The Tianmen Gorge is the centrepiece of Yuntaishan: a deep canyon carved through layered Precambrian rock by a stream that produces the park's signature waterfall at its head. The gorge walls shift from pale grey limestone near the top to vivid rust and burgundy quartzite lower down, the colour bands recording ancient changes in the composition of the seabed from which they were eventually pushed up. Walking the gorge floor, with canyon walls rising over a hundred metres on each side, gives a visceral sense of the geological time encoded in the rock.
The waterfall itself drops 314 metres into the narrow head of the gorge. In spring and after summer rains the volume is impressive; in winter it can reduce dramatically, and in very cold weather sections freeze into dramatic ice formations. The walk from the park's shuttle bus terminus to the waterfall base takes about forty minutes along a well-maintained path with intermittent steps. Early morning arrivals get the best light and significantly thinner crowds.