Phia Oac – Phia Den National Park – Cao Bang’s Green Roof
In western Cao Bang, a mountain region enjoys cool weather year-round. Mist drifts across moss-covered forests, and in winter, frost sometimes coats the branches in white. The French chose this area as a retreat in the early 20th century. Today, it is Phia Oac – Phia Den National Park, home to rare primary forests and one of the region’s most appealing destinations for nature lovers.
Where is the national park?
Phia Oac – Phia Den National Park is located in the former Nguyen Binh District, with its central area in Thanh Cong Commune. In July 2025, the new Thanh Cong Commune was formed by merging Quang Thanh and Thanh Cong communes.
The national park is about 73 km from Cao Bang City and lies within the UNESCO Non Nuoc Cao Bang Global Geopark.
From a French retreat to a national park
The Phia Oac – Phia Den mountain region was discovered and developed as a retreat by the French in the early 20th century. Today, visitors can still find the scattered ruins of old villas among the pine forests.
On January 11, 2018, Phia Oac – Phia Den National Park was established on the entire area of the former nature reserve. It is classified as an IUCN Category II protected area (national park).
Size and terrain
The national park covers 10,593.5 hectares, including 8,146.6 hectares of natural forest. Most of the area lies between 700 and 1,950 meters above sea level.
Several peaks here rise above 1,000 meters:
- Phia Oac: about 1,931 meters, the second-highest peak in Cao Bang and the highest point of the Ngan Son – Yen Lac arc.
- Niot Ti: 1,574 meters.
- Tam Loang: 1,446 meters.
- Phia Den: 1,391 meters.
- Ki Doan: 1,165 meters.
Phia Oac and Phia Den are the two best-known peaks and give the national park its name. Phia Oac is known as the “roof” of western Cao Bang Province.
A biodiversity treasure trove
Phia Oac – Phia Den is recognized for its rich biodiversity, including rare remnants of primary moss forest, a distinctive highland ecosystem found in few other places in Cao Bang.
Scientists have identified 78 threatened plant species from 34 families here. The park is also rich in medicinal plants.
Moss forest – a fairytale landscape
As you climb higher, the trees grow shorter and the moss gets thicker, blanketing trunks and branches. This is a distinctive type of high-altitude “dwarf forest” or “moss forest.” In the mist, these forests look like something straight out of a fairytale.
The four seasons at Phia Oac – Phia Den
Winter (December–February): The season for cloud seas and frost. During severe cold spells, ice may form on Phia Oac’s summit, coating the branches. Cloud season lasts from December to March, with thick banks of cloud especially likely to drift down over the forest at dawn or dusk in February.
Spring: The forest bursts into leaf and flower, while hillsides along the road through Nguyen Binh turn white with bauhinia blooms.
Summer: Cool weather, blue skies, and white clouds make this an ideal escape from the heat. It is also when the hydrangeas bloom at Kolia.
Autumn: Clear skies and gentle sunshine make it a lovely time for cloud watching and taking in the scenery.
What to do at Phia Oac – Phia Den?
Climb Phia Oac Peak
From the foot of the mountain, you can ride or drive about 5 km to the summit. A Vietnam Voice radio transmission tower stands at the top. Set out early to watch the sunrise and catch the clouds, or stay until late afternoon for sunset.
Walk through the moss forest
Pull over at a moss-covered stretch of forest on the way to the summit, then walk for a few minutes to take in the quiet and cool, damp air of the old-growth forest.
Discover French-era relics
- Phia Den Red Villa: the ruins of a two-story stone villa tucked among the pine trees.
- Vong Tien Cung Shrine: an old shrine built in 1939 and linked to a legend about fairies.
Immerse yourself in local culture and unwind
- Kolia Organic Farm: Cao Bang’s first organic tea hill, with a hydrangea garden and camping area.
- Ban Phuong Bamboo Forest: a lush grove of tall bamboo at an altitude of over 1,000 m.
- Hoai Khao Community Tourism Village: a Dao Tien village known for its yin-yang tiled roofs, beeswax-resist printing and silverwork.
- Quang Thuong Community Tourism Area: a place to stay amid the mountains.
Find the best photo spots
- Beautiful tung tree: a photo spot when the tung trees bloom in March and April.
- Hon Da Song Ao and Phan Thanh Grass Hill: green grassland and a rock outcrop among the hills.
- Co Be Then Shrine: a sacred old shrine nestled in the mountains.
Suggested 2-day, 1-night itinerary
Day 1: Travel from Cao Bang City to Nguyen Binh. Visit Ban Phuong Bamboo Forest, the Red Villa and Vong Tien Cung Shrine. In the afternoon, head to Kolia Organic Farm for a stroll through the tea hills and an overnight stay.
Day 2: Get up early to catch the clouds at the summit of Phia Oac, then walk through the moss forest. Have lunch at Kolia, then visit Hoai Khao Village or Phan Thanh Grass Hill in the afternoon before heading back.
Visitor tips
- Dress warmly: Temperatures in the mountains are much lower than in the city. In winter, bring a puffer jacket, gloves and a wool hat.
- Take care on mountain roads: The roads have many bends and can be shrouded in thick fog. Drive slowly, turn on your lights and sound your horn at bends. When icy, the road surface is very slippery.
- Protect the protected forest: Don’t break branches, strip moss, pick medicinal plants or hunt wildlife. Avoid lighting fires carelessly.
- Follow the rules set by the national park management and in restricted areas.
- Take your rubbish with you to help preserve the old-growth forest.
- Check the weather before you go, especially during the rainy season and cold snaps.
Final thoughts
Phia Oac – Phia Den National Park is more than a protected forest. It is home to fairytale moss forests, cloud-covered peaks, French-era relics and the cultural heritage of the Dao and Tay people. Here, you can slow down and breathe in nature, and see why this place is called the green “roof” of western Cao Bang.
