Look at the water and the town makes sense. The Srepok rises among the Central Highlands of Vietnam, in Dak Lak province, and runs 405 kilometres - 281 of them inside Cambodia - to meet the Sesan about 37 kilometres above the Mekong. The Sekong travels 480 kilometres from the mountains near Hue in central Vietnam and joins the same river roughly eight kilometres further down. The Sesan then delivers the whole accumulated load into the Mekong at Stung Treng.

Three major tributaries and the mainstream, gathered within an afternoon's paddling of one another. Local promotion calls it the Mekong plus three. Hydrologists call it the 3S basin and worry about it constantly, because everything that happens on those three rivers - dams, deforestation, sediment, fish - arrives at this town before it goes anywhere else. Hundreds of small islands are scattered through the river here, and hikes up the surrounding hills give views north toward the 4,000 Islands, where the Mekong spreads itself across the Lao frontier.

Wikivoyage is blunt about it: the word for Stung Treng is outpost. Around 29,665 people lived in the town at the 2009 census, in a province of some 176,488 across 11,092 square kilometres - the eighth largest province in Cambodia and one of the emptiest. The town is small enough to cross on foot, and the handful of motodops will run you anywhere in it for a couple of thousand riel.

Most travellers are only passing through, aiming north for the Laos border or south for Kratie, and the guidebooks send them on to Banlung and Kratie for anything resembling an itinerary. That undersells the evenings. The town's honest attraction is the river at either end of the day - sunrise and sunset over the water, a hammock, a bottle of Angkor beer, and no particular reason to move. A weaving co-operative at the north end of town turns out fabrics and patterns worth the walk. Cheap guesthouses cluster along the riverfront and the street immediately behind it, from about three US dollars a room, though a few dollars more buys considerably better.

Highway 7 south to Kratie is fully paved and takes four to five hours, a good deal longer in the rainy season. The road north to the Lao border has been a different proposition - as of 2019 it alternated between stretches of pavement, stretches of gravel, and stretches of bumpy former pavement. A bridge to the west bank opened in August 2014. Buses for Phnom Penh leave around 07:00 from somewhere in the town centre, the exact spot depending on the company, at ten to fifteen dollars; Kratie costs three.

Northbound travellers should know the routine. Through minibuses change vehicles here; passengers walk across at Nong Nok Khiene and pick up a Lao minibus on the other side. Drivers have been known to abandon passengers at the Dom Kralor crossing, which is a good argument for buying a ticket all the way to your final destination. At the changeover, someone will explain that Laos is a communist country where US dollars are useless and ATMs do not exist, then offer to solve the problem at a punishing exchange rate. None of it is true. The Lao visa on arrival costs forty dollars and one passport photograph, no middleman required, plus an unreceipted two-dollar stamping fee that was still being collected in 2024.

Something has gone out of this stretch of the Mekong. Until February 2022, Stung Treng was one of the few provinces in the world where you could see Irrawaddy dolphins in the wild, in pools near the Laos border. That population has almost certainly vanished, killed off by illegal fishing. The species survives downstream - roughly 105 animals along a protected reach running up from Kratie - but not here, and the loss registers in a place where dolphin-watching was among the few things worth stopping for.

What remains is the wetland. On 23 June 1999 the middle stretches of the Mekong north of Stung Treng were designated a Ramsar site of international importance: 14,600 hectares of braided channels, rapids, islands and seasonally flooded forest, running up to the Lao frontier. It is the finest thing in the province to give a day to. The Mekong Discovery Trail that once organised trips through it lost its funding in 2012 and folded, and local operators have since picked up something of the same work. The river did not notice either way. It is still there, four waters deep, exactly where the map put it.