This gate marks the limits of the kingdom of Mustang. An ancient salt trade route that connected the Asian continent from north to south once passed through this door. A forthcoming road to Mustang will soon link China and Nepal. Mustang, Nepal, 2014 (David Rengel)

Sheltered by some of the highest mountains in the world — Annapurna and Dhaulagiri — and bordering China on the Tibetan plateau, hides an ancient kingdom called Mustang, or Land of Lo. The kingdom is often confused with the mythical Shangri-La. The capital of the Mustang kingdom, Lo Manthang, is home to the Loba people, and its walled city is considered by some scholars to be the best preserved medieval fortress in the world. It is a candidate to become a UNESCO World Heritage site.

Thanks in part to its ancestral location — and because it has been forbidden to foreigners until as recently as 1992 — Mustang has retained its ancient culture. Though its capital is located in Nepal, it is one of the last strongholds of traditional Tibetan life left in the world. It remains a restricted region that is difficult to access. Foreigners must obtain special permits and pay high rates to visit it.

Photographer David Rengel visited the region recently to document the culture and observe its long-preserved way of life. Part of the project was realized while he began filming a documentary alongside producer and director by Larry Levene called “The Last Lost Kingdom” for the production company Es.Docu.

The lower part of Mustang yields more moist land and is rich in vegetation, while the more arid land in upper Mustang makes agricultural life a bit harder.

For centuries, caravans roamed the Kali Gandaki gorge between regions of Tibet, China and India with salt, yak wool, cereals, dried meat, spices and other goods on the so-called Salt Road. A road is being built along this route that will directly connect Mustang with China. When the road is completed, it will become one of the most accessible corridors of the Himalayas, and Mustang’s inhabitants’ lives may rapidly change with the influx of foreigners. Many of the young Loba people are waiting expectantly and anxiously for the road’s completion, but many older residents are hesitant about what it will mean for their culture and identity.

Ana Baba is a sadhu, a Hindu practitioner who follows the path of penance and austerity to attain enlightenment. He has decided to go the kingdom of Mustang to meditate. Mustang, Nepal, 2014. (David Rengel)

The new road linking China and Nepal is passable in lower Mustang. The road makes it easier to for vehicles to cross mountains more than 9,000 feet tall. Mustang, Nepal, 2014. (David Rengel)

A man wears a funerary mask of gold and silver that is about 1,500 years old. It was found in a box inside a cave in Sam Dzong, a village that has been the last stop before the border with Tibet and China. 2014. (David Rengel)

Sandup Gurung and his son Sirin Gurung thresh by hand the buckwheat and oats that they collected the previous day. They will used it for roofs, baskets and feed. Mustang, Nepal, 2014. (David Rengel)

Two Loba women carry heavy adobe bricks for building a house. Houses in Mustang are constructed using bricks made of stone and earth. The foundations are filled with debris and the walls with mud. In the background is the ancient fortress of the village of Garphu. Mustang, Nepal, 2014. (David Rengel)

A tributary of the Kali Gandaki River forms during the summer rains in this canyon. In the background are the great mountains of the Himalayan range. 2014. (David Rengel)

Rinzin Wangmo is the first traditional doctor to graduate from Lo-Kumphen Mentsi Khang School of Tibetan Medicine in Lo Manthang. The Loba doctors were also regarded as chemists, botanists and magicians, to some extent. 2014. (David Rengel)

A portrait of the king and queen Raja Jigme Dorge, and his wife, Sidrol Bista, of Mustang in a room of the Royal Palace. The monarchy was abolished on Oct. 7, 2008, by order of the new government of Nepal. 2014. (David Rengel)

The cave of Jhong has a maze of corridors. In the mid-1990s, Nepali archaeologists, in collaboration with the University of Cologne, began exploring the caves where they found several manuscripts and wall paintings that represent the history of Buddhism. Mustang, Nepal, 2014. (David Rengel)

A group of women dressed in traditional garb restore walls at Tupchen Gonpa monastery. They receive three months of training and constant supervision by experts from the American Himalayan Foundation. 2014. (David Rengel)

This holy book with gold lettering was found in the Tasarang Palace’s library. The library contains many sacred books, including the Jhun, a treasure of Tibetan culture transcribed from Sanskrit. Of the three copies in the world, two are kept in the library. Mustang, Nepal, 2014. (David Rengel)

Snow leopards were mummified in the gateway of the monastery of Chuksang. The animals, once believed to ward off evil spirits, are now an endangered species. Mustang, Nepal, 2014. (David Rengel)

These masks, called of figures called chitipati, are used in the traditional dance of the “skeleton lords.” They represent the ephemeral nature of things. Mustang, Nepal, 2014. (David Rengel)

A white horse grazes near a gate that marks the limits of the kingdom of Mustang. The new road will pass through this gate to link China and Nepal. 2014. (David Rengel)