Dark and Bright Cave

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Green Sea Valley

Located in the emerald waters of Lan Ha Bay, Vietnam, lies a hidden gem that you should not missed.  Dark and Bright cave, also known as Hang Sang Toi in Vietnamese, is a natural under-water cave that lie in most of the itinerary of cruises sailing this area. 

In this article, let’s CruiseInHalongBay.com show you why this beautiful cave worth your attention. 



Dark and Bright Cave is located inside Lan Ha Bay, an extension of Halong Bay. It’s a part of the Cat Ba archipelago and only about 30 minutes boat ride from the main island. Dark and Bright Cave is also surrounded by lots of area’s sightseeings, such as Sung Sot Cave, Cat Ba National Park, Van Boi Beach or Viet Hai village. Its conveniently location make is quite easy to see multi-sightseeing of Halong Bay in just 1 visit. 


The Beauty of a Dark and Bright Cave


Unlike many others caves in Halong Bay with exquisite stalagmites and stalactites, Dark and Bright Cave is famous for its unique structure. The Dark & Bright Cave is a combination of two, as its name suggests, Dark Cave and Bright Cave.


The Dark Cave

The Dark cave, come with no surprise, is quite dark. The cave is about 100m length, with its highest point measured only about 2 meters from the water surface. It’s very light-tight, with nearly non-existent natural lights. Dark Cave is being covered by the waters most of the time during the years, making it extremely hard to visit. It was used to be open for tourist in the past, but now, because of visitors safety concerns, the bay authority decided to forbid all travelers to enter, even when the cave is revealed. 

Dark Cave
Dark Cave is underwater for most of the time – Source: Internet

The Light Cave

The Light Cave is the main attraction of the area. Comparing to its brother, Light Cave is much bigger with 3m in height, 4 meters wide and most importantly, available all year round. Despite of being bigger than the others, it’s still impossible to visit by big boat or cruises. You’ll have to take kayak or bamboo boat to get through the cave. Inside Light cave, you could find many small holes from the ceiling, which allow sun to shine through and when its reflect with the water surface, make the entire cave sparking, like a heaven on earth. 

However, the surprise still waiting for you ahead. After getting our of the cave, you will meet a huge green lagoon surrounded by giant mountain limestones, seems to be separated with the busy bay. Thanks to the limestones, the lagoon in Light Cave become extremely quiet and peaceful. Let your boat or kayaking floating tirelessly above the emerald water, enjoy the quiet and tranquil atmosphere will become your most relaxing moment in Halong Bay. 


Taking kayaking into Bright Cave
Taking kayaking into Bright Cave – Source: Internet


How to get there


As Dark & Bright Cave located in Lan ha Bay, an extension part of Halong Bay, you’ll have to travel there first. Take a look at our guide Halong Bay transportation. 

Once getting to Halong Bay, the only way to get to Dark and Bright Cave is by cruise. Normally, an overnight cruise would be an ideal option, as besides Dark and Bright Cave, these cruises will take you to explore other famous destinations in the surrounding area.

However, if you’re tight on time and budget, a day cruise could also help you explore this beautiful wonder. In order to take the day cruise, the first step is to reach Cat Ba Island. You can take a ferry or speed boat from Hai Phong or Halong Bay directly to Cat Ba Island. Once you arrive at Cat Ba Island’s Beo Wharf, head over to your hotel and book a tour package that includes a trip to Dark and Bright Cave. If you prefer going solo, rent a boat for the day from Beo Wharf and navigate towards Lan Ha Bay yourself.

A day cruise to visit Halong Bay usually lasts from 4 to 6 hours. Boat tour ticket prices range from 500,000 VND per person to 1,000,000 VND per person, depending on the boat or itinerary you choose. A lot of exciting things are waiting for you to discover.

If you’re keen on taking an overnight cruise that covers Dark and Bright Cave, take a look at our collections of Lan Ha Bay Cruises.


The best time to visit


The best time to visit Dark & Bright Cave is from April to July, when the temperature range is from 25 to 30 degrees Celsius. The weather is favorable for water activities like swimming, kayaking, or snorkeling. The sky is also quite clear during this time, and if you’re lucky, you might have a chance to see a magnificent sunset in the area.

lan ha bay during summer months
The entire area is sunny during summer months – Source: Hoang Ngan

Extra tips: Be aware that there will be occasional rain and typhoons, especially during June and July, so check your forecast before planning. 

For further information, here’s our weather guide of Halong Bay


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