Nui Thung Mountain – Untouched Angel Eye of Cao Bang Stone Plateau

Tucked away in the heart of Cao Bang's majestic stone plateau, Nui Thung Mountain – also known as Angel Eye Mountain Cao Bang (Nui Mat Than) – remains one of Vietnam’s most breathtaking and pristine natural landscapes. What makes it so unique, and why do travelers call it a sight from another world? Let’s uncover the mystery behind this enchanting destination.

1. Where is Nui Thung Mountain Located?

Address: Cao Chuong Commune, Trung Khanh District, Cao Bang Province (formerly part of Quoc Toan Commune, Tra Linh District).

Nui Thung Mountain is located in the Thang Hen Lake area within the Non Nuoc Cao Bang UNESCO Global Geopark. Situated approximately 30 kilometers from Cao Bang City, the route to Nui Thung typically begins from the city center, following provincial roadways that wind through lush valleys and limestone landscapes.

The mountain’s nickname, Angel Eye Mountain, comes from its most striking feature: a perfectly round hole, about 50 meters in diameter, piercing through its peak like a giant eye. This unique mountain is not only a geological marvel but also a growing hotspot for ecotourism and adventure travel.

Nui Thung captivates visitors with its massive circular hole carved through the limestone peak (Source: Internet)

Location of Nui Thung mountain on Google Maps (Source: Internet)

2. History and Cultural Significance of Nui Thung Mountain

Geologically formed over 300 million years ago, Nui Thung Mountain is believed to have once been a dry cave. Over time, tectonic activity lifted the cave, shaping it into the impressive limestone formation we see today. These same geological forces also sculpted the surrounding region into a dramatic karst landscape filled with cone-shaped and tower-like mountains, interspersed with more than 30 lakes at altitudes ranging between 650 and 700 meters.

Nui Thung lies within the Thang Hen lake complex, which was officially recognized in 2016 by Vietnam's Institute of Geosciences and Mineral Resources as a geological heritage site of international significance. The area’s rare phenomenon of “intermittent lakes” – natural lakes that fill and drain seasonally – is considered a global rarity in karst terrain, which contributed to its exceptional geological and environmental value.

Nui Thung Mountain, estimated to have formed over 300 million years ago, was originally a dry cave (Source: Internet)

The region’s dramatic karst landscape and seasonal flooding have long shaped local life in Ban Danh village, home to the indigenous Tay people. Generations have relied on farming, fishing, and livestock grazing in the lush valleys surrounding the mountain.

During the rainy season, the area transforms into a vast inland lake, where locals use rafts to fish and guide tourists. Recognizing its natural and cultural importance, the site was listed as a National Scenic Landscape by Vietnam’s Ministry of Culture, Sports and Tourism in 2021.

3. Unforgettable Experiences at Nui Thung Mountain

Beyond its geological wonders, Nui Thung offers visitors a rare opportunity to immerse themselves in nature through unique, hands-on experiences.

3.1. Capture The Stunning Scenery

Photography at Nui Thung is a dream come true, especially for those seeking raw, natural beauty. The best shots are taken from the valley floor, looking up at the iconic “eye” in the mountain. For sunrise enthusiasts, timing your visit just as the first rays of light pass through the hole creates a surreal, golden-hued spectacle.

Tips for photographers:

• The most magical light is in the late afternoon, usually between 04:30 PM and 06:00 PM, especially from September to February, when the sun rises at a lower angle in the sky.
• Phone setting: Use HDR mode and tap to focus on the eye-shaped hole. Lower the exposure slightly to avoid blown-out highlights.
• DSLR/Mirrorless setting: Shoot with a wide-angle lens (~16–35mm), use aperture f/8–f/11 for landscape sharpness, and a tripod if capturing long exposures at dawn or dusk.
• Bring a tripod if you want to do long exposures of sunrise or capture the stars at night.
• For portraits: Shoot with a shallow depth of field (f/2.8–f/4) to blur the background slightly, placing the person off-center with the “eye” visible in the backdrop.
• Try a silhouette shot: Have your subject stand in front of the “eye” at sunset for a dramatic effect.

Nui Thung, with its iconic natural arch resembling a giant eye, is a dream come true for landscape photographers and nature lovers (Source: Internet)

Arrive early, find your spot, and let nature do the rest (Source: Internet)

Taking photos and checking in at Nui Thung is a completely free experience (Source: Internet)

Capturing Nui Thung is a beloved activity of many tourists (Source: Internet)

Tourist reviews of the beautiful scenery of Nui Thung Mountain (Source: Internet)

3.2. Embark on A Camping Adventure

Camping at Nui Thung is an unforgettable way to immerse yourself in the mountain’s breathtaking beauty. The best part is that there is no entrance fee to enter the valley, feel free to bring your own camping gear!

You can choose a quiet spot in the vast grasslands, either near the mountain to enjoy the sunrise or closer to the stream for a more peaceful experience. For those who prefer a more comfortable experience, local service providers offer tent rentals, prepared meals, and campfire setups, but these services do come with a small fee (about USD 30 per person).

The flat terrain makes it easy to pitch tents, even for first-time campers (Source: Internet)

Tip:

• The best time for camping is from September to March (lunar calendar), as this is the dry season in Cao Bang.
• Bring insect repellent and warm clothes, as temperatures can drop significantly at night.
• Always respect the environment by cleaning up after yourself and avoiding any damage to the natural landscape.

Review of tourists about camping experience at Nui Thung (Source: Internet)

3.3. Discover The Hidden Waterfall Deep Within The Valley

The hidden waterfall within Nui Thung’s valley is another must-see for visitors. Tucked away among the trees, this small but stunning waterfall provides a peaceful escape and adds an extra layer of charm to the landscape. During the rainy season, the valley becomes a massive lake, and the waterfall merges with the rising waters, creating a stunning view of water cascading into the basin.

In contrast, during the dry season, the waterfall stands out as a serene feature against the backdrop of lush meadows and grazing livestock. The waterfall is easily accessible on foot through gentle trails, making it suitable for most visitors. And best of all, visiting the waterfall is completely free of charge.

The waterfall is accessible on foot by following the small trails running through the valley (Source: Internet)

Share of tourists about the peaceful landscape hidden deep in the mountain (Source: Internet)

3.4. Drift Downstream on A Bamboo Raft or Adventure on a SUP

While camping at Nui Thung, you can take part in extra activities such as stand-up paddleboarding (SUP), typically priced at around 50,000 VND (~USD 2) per person. These activities allow you to explore the surrounding areas of the lake with friends or family while enjoying the calm atmosphere and scenic views.

Tips:

• For the best experience, visit in the morning when the lake is calm and the landscape is illuminated by soft sunlight.
• Visitors should come in the rainy season (from April to August) when the lake is at its fullest.
• Be prepared for rough roads leading to the area, as the path can be challenging in the rainy season for both motorbikes and cars.

When the summer rains arrive, the valley transforms into a massive inland lake, turning Nui Thung into a water-world paradise (Source: Internet)

While there is no entrance fee to access this area, engaging in activities like SUP or bamboo rafting will require a small fee (Source: Internet)

4. How to Reach Nui Thung Mountain?

Nui Thung Mountain lies around 30 kilometers north of Cao Bang City, and travelers can reach it by either motorbike or car. For those opting to ride a motorbike, you can easily rent one in the city and follow National Road QL3 heading northward. Once you ascend Ma Phuoc Pass, turn left and continue for another 10 kilometers. Keep an eye out for a small sign on the left-hand side, which marks a narrow road leading into the valley. Once you're inside, you’ll find more signs directing you toward the mountain and the nearby lake.

Motorbike rental is often the preferred option for many travelers due to the road conditions (Source: Internet)

There are two main routes to access the valley:

• The first route, located near Thang Hen Lake, is easier to navigate. However, you will need to park your vehicle at the top of a hill and walk about 300 meters downhill to reach the valley.
• The second route, on the backside of Nui Thung, is closer to Tra Linh Town but involves a steep incline. During rainy weather, it can be challenging for cars to make it up and down the slope.

Tips:

• Cars can reach the site directly, but the path is only wide enough for one car, so if you encounter a vehicle coming from the opposite direction, passing can be extremely difficult.
• It's recommended to negotiate prices clearly when hiring a local motorcycle taxi.
• Avoid using Google Maps to navigate, as it can provide incorrect directions. Instead, ask local residents for guidance, as they can offer the most accurate route.
• No entrance fee is required to visit the mountain, and the area is free to access.
• There are informal stands along the route selling drinks at affordable prices, so feel free to stop and enjoy the scenery.

The journey to Nui Thung is a rewarding experience, offering scenic views of lush green meadows and rolling hills (Source: Internet)

5. Best Time to Visit Nui Thung Cao Bang

To make the most of your adventure to Nui Thung, it’s essential to consider both the time of day and the season. The mountain offers different charms throughout the year and even shifts dramatically in atmosphere depending on the hour.

1 - Time of Day

The best time to visit Nui Thung is in the afternoon, between 04:30 PM and 06:00 PM. This is when sunlight aligns perfectly to stream through the iconic hole in the mountain – the “eye” – creating a breathtaking natural spotlight.

Avoid visiting during midday when the lighting is harsh and the valley may be too hot for comfort. Likewise, late evening visits are not recommended, especially if you're unfamiliar with the terrain, as the narrow roads become more difficult and unsafe to navigate in low light.

For the most breathtaking views and photo opportunities, aim to visit between 04:30 PM and 06:00 PM (Source: Internet)

2 - Time of Year

The best time to explore Nui Thung is during the dry season, from September to March, which is ideal for outdoor activities like hiking, photography, and camping. During this time, the valley transforms into wide green meadows dotted with herds of grazing horses and cattle, perfect for a peaceful escape into nature.

In contrast, the rainy season from May to September turns the entire valley into a vast natural lake, which can be both stunning and challenging. While some may find the waterlogged scenery magical, accessibility becomes more difficult, and certain trails may be flooded. For the safest and most rewarding experience, try to avoid the peak rainy months of July and August.

In the dry season, the area still retains its raw, majestic beauty with open grasslands and vast views – ideal for camping or hiking under clear skies (Source: Internet)

6. Essential Travel Tips for Exploring Nui Thung Mountain

To make the most of your adventure at Nui Thung Mountain, here are some essential tips to ensure a smooth, safe, and memorable trip:

• Follow local signs carefully: Look out for directional signs around the area to avoid entering unsafe zones, especially during the rainy season when the valley can flood or become slippery.
• Consider hiring a local guide: Unlike a typical package tour, a local guide offers a more personal and enriching experience with cultural insights, knows hidden trails, and ensures a smoother and safer journey.
• Uncover local culture in Ban Danh village: Explore the daily life of the Nung and Tay ethnic groups and support local community-based tourism.
• No public restrooms available: There are no mobile toilets at the site. It's best to use restrooms in Cao Bang City or near Thang Hen Lake before your visit.
• Don’t rely solely on Google Maps: When heading to Thang Hen Lake, look for a sign to “Nui Mat Than” (God’s Eye Mountain) on your right. GPS may mislead you – ask locals for the correct route.

Google Maps often misplaces the exact turnoff, so asking locals for directions can save time and frustration (Source: Internet)

7. Explore Nearby Hidden Gems Around Nui Thung

The surrounding area of Nui Thung offers several lesser-known attractions that are equally enchanting. If you have time, here are some nearby hidden gems worth exploring:

Natural beauty and cultural heritage surrounding Nui Thung Mountain (Source: Internet)

Nui Thung Mountain is a picturesque escape in Cao Bang. From sunrise magic piercing through the legendary “Mountain Eye” to serene bamboo raft rides on crystal-clear lakes, every moment here promises something unforgettable. With nearby hidden gems like Thang Hen Lake, Nam Tra Waterfall, and Ngu Lao Heaven Gate, your adventure doesn’t end at the mountain – it only begins.

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