Detlef Berg discovers history, natural wonders and a way of life along the banks of the great waterway.
As described in the 1933 novel Lost Horizon by British author James Hilton, the fictional Shangri-La is a mystical and earthly paradise where its population is permanently happy.
The modern Shangri-La is in the Chinese province of Yunnan where the Mekong River, the largest in Southeast Asia, flows down from the Tibetan highlands before meandering its way through southwestern China.
Named Zhongdian until 2001, Shangri-La is one of many cities built along the Mekong and was obscure until its renaming, which was aimed at attracting foreign tourists.
Despite its cynical rebranding, Shangri-La is worth a visit, not least to see the Sungtseling Monastery, where about 400 Buddhist monks live high above the city.
The Mekong is navigable from Jinghong downstream. It forms a 200km-long natural border between Laos and Myanmar.
At the Golden Triangle where Thailand, Myanmar and Laos meet, you can visit the Hall of Opium to see how opium poppies are grown and illegal drugs were manufactured.
Funded by the Thai royal household, the museum is part of a project aimed at ending the local population's dependency on the drugs trade by supporting economic alternatives.
After the Golden Triangle, the Mekong broadens and tourists join cruise boats going towards Vietnam. "The Mekong is not easy to navigate," explains captain Khampet, who decorates his boat with flowers and rice as part of an age-old ritual to fend off evil river spirits.
The greatest problem is the huge variation in river level by up to 12m.
During the dry season, only a narrow channel is navigable. Rapids have to be avoided in the rainy season.
Not surprisingly, the captain refuses to travel at night and the ship is anchored when darkness falls and passengers enjoy an evening meal of spicy chicken soup cooked with ginger and served with rice and vegetables.
The ship lifts anchor in the early morning and, although the thick jungle reaches the river's edge, at times it is still possible to see the small villages where local farmers live.
Occasionally a working elephant springs into view as it drags a teak trunk towards the river.
The boat anchors again near Pak Tha in Laos to allow a visit to a village that seems stuck in the Middle Ages. Children run around near-naked and look on in wonder as the group take countless photographs of their surroundings.
A few kilometres further downriver we receive a warm welcome from village elders at Thanoon before the journey begins again.
"Pak Ou!" shouts the captain as he draws our attention to a rocky outcrop ahead.
He steers the boat directly at the imposing cliffs. Steep steps guide our group towards a limestone cave that houses thousands of Buddha statues and is considered one of the country's most important pilgrimage sites.
"They guard the river, its spirits and its magical powers," the captain explains.
Luang Prabang, the former royal city of Laos, lies 30km further downstream and by mid-morning hundreds of monks are out and about with their begging bowls.
Women come out of their houses and fill the bowls with rice and other food as the procession slowly winds its way through the city.
With its golden temples, royal palace and more than 600 protected buildings, the Unesco World Heritage site of Luang Prabang is one of the highlights of any trip to the Mekong.
In the Laos capital Vientiane, the end point of the nine-day cruise, an afternoon is enough to take in That Luang, a Buddhist stupa, and the city's triumphal arch.
At Vat Phou in the south ofLaos there is a 1500-year-old Khmer temple. The unusually wide Khone Phapheng waterfalls are the final tourist attraction before entering Cambodia.
Siem Reap is a must-see destination before the river winds into southern Vietnam. The farmers in this area enjoy rich harvests, thanks to the sediments deposited across the Mekong Delta by the river before it empties into the South China Sea.
's 'Treasure of China' tour lasts 15 days, with prices starting from $1499.