Five limestone and marble outcrops rising abruptly from the flat coastal plain 9 km south of Da Nang's city centre — one of the stranger pieces of geology on Vietnam's central coast. The largest hill, Thuỷ Sơn (Water Mountain), has a staircase to the summit (there's also a lift) and a labyrinth of Buddhist caves and grottoes, some open to the sky through fissures in the roof where shafts of light fall on golden Buddhas.
The Huyền Không cave, reached through a narrow passage, is the largest — an enormous natural cathedral with stalactites and an altar carved into the far wall. Outside the cave complex, the summit pagodas have fine views over My Khe Beach and the resort coast south toward Hoi An. The surrounding village at the base has been carving marble and stone for centuries; the souvenir stalls are unavoidable but the craft is genuine.