The defensive circuit at Hailongtun runs nearly 6 kilometres and incorporates nine gate passes — nine distinct chokepoints up the mountain, each designed to be held by a small number of defenders against a much larger force. The walls are built directly from the stone of the mountain itself, in places following natural cliff edges so steeply that the fortification and the geology become indistinguishable. You can walk the full circuit in two to three hours; the views from the upper walls extend over the Guizhou plateau and toward the Sichuan border.
The stonework is Ming-era construction at its most practical — massive dressed blocks, no mortar, fitted so tightly that the joints remain stable after four centuries of freeze-thaw. The archer towers, though roofless, give a clear sense of the original sightlines: from the highest positions, the entire approach up the mountain is visible, and there would have been no way to move a large force toward the upper gates without being seen from the moment they entered the valley.
The inner area of the fortress contained barracks, granaries, armories, and water cisterns — the Yang family designed Hailongtun to be self-sufficient during extended sieges. Some of the cistern systems are still visible as stone-lined pits in the ground. The granary foundations are among the most thoroughly excavated parts of the site; archaeologists in the early 2000s found grain storage evidence suggesting the fortress could sustain several hundred people for years.