Democratic Republic of Congo - The River Congo has always inspired reverence.

"Our River Congo spills violently into the ocean, which is unable to stop its passage," Engeye Nbondwange, an aging naval officer and amateur historian, says as he vigorously gesticulates on the beach at Banana Point, a spit of land where the land, river and ocean collide.

"Our River Congo discharges 50,000 cubic metres of water per second into the Atlantic Ocean," he says, as he marvels at the 160km-long gorge the powerful river has bored into the seafloor over thousands of years.

Aided by a homemade map and wooden stick, Nbondwange has become a semi-permanent fixture at Banana Peninsula, a sandy piece of land that juts into the mouth of the River Congo at the southern tip of the country's tiny slither of coastline. He energetically dispenses lessons about the river, which ejects more water into the ocean than any other in the world other than the Amazon.

Banana Penisula has been a naval base since Congo was a Belgian colony. Today, there is little sign of any operational military hardware but hundreds of impoverished soldiers are still stationed here. Anyone wishing to reach the beach has to hand over a couple of dollars to a bored recruit to pass through the roadblock at the camp's entrance.

While Nbondwange fizzes with enthusiasm as he tells the river's stories, most of the men here have little to do other than sit outside their dilapidated houses.

A variety of vessels - from oceangoing container ships to motorboats weighed down by smuggled petrol to fishermen's wooden canoes - can be seen at the river's mouth. The larger boats are headed upstream to the town of Boma and the city of Matadi to offload their goods.

As Nbondwange moves from the river's geography to its history, he begins to tell the stories of the white men who arrived at the river's vast estuary more than 530 years ago.

Slave trade

First among them was Diogo Cao, a Portuguese captain who made his way down the coast of West Africa in 1482, becoming the first European to come across the River Congo.

Dispatched on a second voyage by the Portuguese king two years later, Cao forged friendly relations with the manikongo, the ruler of the Kingdom of Kongo, an independent state founded in the late-14th century. The kingdom included a lengthy section of the river and stretched hundreds of miles inland to include parts of today's Democratic Republic of Congo (Congo), Angola, Republic of Congo and Gabon.

In 1491, priests, soldiers, farmers and others sent by the then Portuguese king were welcomed by the manikongo.

Adam Hochschild in his book, King Leopold's Ghost, wrote that the arrival of this party "marked the beginning of the first sustained encounter between Europeans and a black African nation".

This relationship would prove to have a traumatic effect on the inhabitants of this part of Central Africa for hundreds of years.

According to Hochschild, Pende oral historian Mukonzo Kioko described the devastation triggered by the enduring interest of Europeans in his land: "Our fathers were living comfortably … They had cattle and crops; they had salt marshes and banana trees. Suddenly, they saw a big boat rising out of the great ocean … White men came out of the water and spoke words that no one understood … From that time to our days now, the whites have brought us nothing but wars and miseries."

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Slavery had already existed in Kongo, but the Portuguese, with the connivance of the kingdom's elite, introduced its domestic marketplace to the rapidly growing international slave trade. African middlemen sold slaves to the Portuguese, which were then shipped mainly to the plantations of Sao Tome or Portugal, and later to Brazil, the Caribbean and North America. By the 17th century, 15,000 slaves a year were leaving Kongo.

In 1816, a British Royal Navy captain, James H Tuckey, led an expedition up the River Congo. He was sent by the British government to locate its source, but Tuckey and much of his crew died of fever after giving up their mission.

Prior to his death, Tuckey encountered slave ships and local merchants who supplied the cargo.

Because some European states had outlawed the trade they had previously exploited, Tuckey wrote in his account of the journey that he had to offer a local chief his "assurances of not coming to prevent the slave trade, or to make war" in order to continue his journey upstream.

Upstream to Boulambemba island and Matadi

Among the places Tuckey came across was Boulambemba, an island a short boat ride from Banana Point through a labyrinth of mangroves.

Today, Boulambemba sits inside a wildlife park where Ranger Pierre Manene hacks his way through the vegetation for several minutes as he makes a path towards an abandoned watchtower and several enormous cannons, which were once trained on the river's mouth to defend Belgian Congo during World War II.

"The Belgians were afraid that the Germans would attack their colony," Manene tells Al Jazeera as he scrambles over the rusty barrels. In the first decade of independence, Boulambemba was repurposed as a political prison.

Less than 160km inland from Boulambemba, the River Congo becomes impassable. This is where Matadi, a major city and Congo's main international port, is located.

Established in 1879, Matadi played an integral part in allowing the European colonists to open up a huge swath of Central Africa and unleash decades of physical and economic exploitation on its inhabitants.

In 1885, European powers granted Belgian King Leopold II private possession of the territory that would become Congo. As his approached the end of his life, Leopold was forced to hand over the state to the Belgian government in 1908, but the colony would exist for another 52 years before Congo gained its independence in 1960.

The architect of the new colony was Welsh-born explorer Henry Morton Stanley, who in the 1870s led a mission across Africa, east to west, and followed the river for 1,600 miles to the Atlantic Ocean.

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Historian Martin Meredith wrote in The Fortunes of Africa that "Stanley's expedition unlocked the entire Congo region [by proving] that beyond the cataracts and canyons that had hitherto blocked exploration inland lay a web of interconnecting rivers, navigable by steamboat, running for thousands of miles into the interior."

The upriver voyages of both Cao and Tuckey had been frustrated by the Yellala Falls, which sits just upstream from today's Matadi. From here, ships are blocked from travelling upstream by more than 30 sets of rapids spread over 290km until Malebo Pool, a wide river basin. Here Stanley established a trading station called Leopoldville on the pool's south bank in 1881, which eventually became Congo's capital of Kinshasa.

Stanley, who understood that overcoming the impenetrable section of the river was the key to profiting from the colony's riches, declared in the late-19th century that "without the railroad, the Congo is not worth a penny."

The railway

Construction of the first railway between Matadi and Kinshasa started in 1890 and took eight years to finish.

It was "a modest engineering success and a major human disaster", wrote Hochschild in King Leopold's Ghost, referring to the thousands of workers from West Africa, the West Indies, Hong Kong, Macau and Europe who died from sickness and accidents during railway's construction.

Before the railway was built, it would take porters nearly three weeks to travel between Matadi and Malebo Pool. After its completion, the journey took just two days and greatly aided what the writer Joseph Conrad called the "vilest scramble for loot that ever disfigured the history of human conscience". Today, the trip takes eight hours.

While the railway was being built, there was a dramatic increase in the global demand for rubber sap due to the invention of the pneumatic tyre.

The Congolese rainforest was full of this newly coveted commodity. Companies, licensed or controlled by King Leopold, brutalised villages by taking hostages, whipping, mutilation and murder to obtain as much rubber as possible at minimum expense.

After years of inactivity, Matadi's colonial-era station has been renovated and painted in the colours of Congo's flag, as has the train which sat on the tracks and has trundled from Kinshasa and back once a week since mid-2015.

In contrast with the battered minibuses which line the road to the Congolese capital, the second-hand carriages are clean and the seats padded. A sharp hoot and, at 7.30am, the locomotive grumbles into action.

The churning river lies below as the train winds around a series of steep cliffs and over a succession of bridges. It runs between walls of rock close enough for passengers to touch before making its way through rolling hills and grasslands.

Kingatoko, Kasangulu, Kisantu, Kenge are all stations along the way to Kinshasa. At each stop, the train transforms into a farmers' market as an army of women and children selling tomatoes, onions, mushrooms, charcoal and watermelons runs towards it. Business is done briskly through windows and doorways.

Congo's rail network, which was a source of pride for the colonists, has not fared well in recent decades. Since the 1980s, much of the country's crucial infrastructure, including its mines and the railways deteriorated and collapsed as Mobutu Sese Seko, who was president for 32 years, sucked dry the productive parts of the economy. The overthrow of the dictator in 1997 heralded not a new dawn, but a civil war that cost millions of Congolese their lives.

Since 2003, most of Congo has been peaceful but the government has largely squandered opportunities to improve the lives of the population, which remains among the poorest in the world. One symptom of the country's dysfunction is how badly connected it is, by road and rail. The Matadi-Kinshasa service stuttered along until 2003 when a train derailed and two carriages landed in the river, killing 11 people. It took nearly 12 years to reopen the route.

Kinshasa

In a dining car on the train to Kinshasa, the smell of the fish being fried by the train's cook, Dadine, is overpowering. Beer bottles are spread across a table occupied by a man and two women. By midday, the trio, drinking steadily, are laughing raucously.

At the back of the train is chief controller Mbala Ndombasa, who sits quietly and unbothered as he does paperwork. He shrugs and smiles when asked why the railway was out of order for more than a decade.

"We didn't have a locomotive," he says, as if explaining something obvious.

Another member of the train's staff says "money, like always" is the reason why the train service was halted for so long.

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The railway may be operating again, but precarious finances are still an existential problem, as they are for the entire Congolese state.

Several days later, at his office in Kinshasa, Valentin Gerengo-N'vene, the transport director at the public company that owns the railway and several ports, says the freight service is dealing with an economic slowdown.

"In the case of passenger traffic, tariffs don't cover the operating costs," Gerengo-N'vene tells Al Jazeera, adding that the passenger train is running at a "chronic loss". The company itself has been plagued by strikes over unpaid salaries.

Back on the train, some eight hours after its departure from Matadi, Kinshasa comes into view. The slums of corrugated iron and timber built atop compacted rubbish suddenly give way to the pristine central station.

The Gare de l'Est station is at one end of Gombe, a riverside Kinshasa commune of pricey restaurants, expatriate housing, foreign embassies and government ministries.

In this gilded domain, Kinshasa's population of at least 12 million is largely severed from the River Congo by high walls behind which lie private ports, ambassadorial residences and multimillion-dollar real estate.

Most Congolese are cut off from the river, and Lieutenant Nbondwange, back at Banana Point, would be sad to see it.