Dong Hang Hanh

Accessible by a hidden entrance that only appears at low tide, Dong Hang Hanh or Tunnel Cave is Halong’s longest grotto, burrowing through Quang Hanh Mountain for nearly 2 kilometres. If you hear a spooky sound, don’t worry, it’s only a ghost. According to legend, three young girls were so engrossed by the beauty of the cave that they failed to notice the rising tide and drowned, becoming water goddesses who can only be heard in echoes.