Passing through Luon Cave, tourists will reach a brackish lake formed by an enclosed group of lime-stone mountains. People believe that the lake once was a deep valley that men used to live in as until these days traces of fossils of fresh-water snails still can be found on the cliffs.

The lake inside is around 1 km2, similar to a stadium, with calm and jade-green surface. On the cliff, pristine setting of ferns, orchids and benjamin fig trees shade the landscape. Once reaching the lake, you will be told to keep the silence, then the boat rower will call out the… golden head monkeys by making strange noise. If you are lucky enough, you will be able to see some of them running to and fro on the trees. Luon Cave is considered as a perfect place to kayaking so if you are a fan of this acitivity, do not miss out this site during your journey in Halong Bay.