Abstract
Karst caves in Tràng An are developed mostly at the foot of limestone mountain cliffs of the Middle Triassic Đồng Giao formation (T2ađg). The caves usually have two inter-connecting entrances, and play the role as a connecting route between closed karst valleys. The cave floors are below the local base level, are flooded all year round and are covered by a layer of sediments. Their ceilings are usually low above the water table. The speleothems in the caves are diverse in shape and size, and are of high aesthetic value. They are clean and are still in the process of formation and development. The caves here are of critical importance in ecotourism activities, therefore an orientation for rational exploitation and use of these ecotourist resources should be adopted to work toward sustainable development.