Where the Danube bends at Tulcea, near the Black Sea in eastern Romania, the river divides. The main body continues along the north of the Delta towards the Black Sea, entering it near Chilia. Several miles southeast of Tulcea, the narrower section, now calling itself the Old Danube, again divides, this time into the Sulina and St Gheorghe branches, which flow between drowsy oxbows, reed beds and lakelets that multiply into infinity as water leaches away through man-made channels into the swelling wetlands.

Sulina is the Delta’s largest town, and the only means of getting to it is still by water. From the river, the Lipovani villages become visible: clusters of floating docks, motorised canoes and blue-and-white-cottages under sharp-hewn thatch, with here and there a tourist hotel for fishermen, built Vegas-style. Descendants of Old Believers who escaped Russia in the 18th century to seek religious freedom among the herons, the few thousand Lipovani are the marshes’ only year-round residents, living from fishing, a little farming and the annual reed harvest. They qualify as one of Europe’s most isolated communities.

The St Gheorghe course of the river is the nobler of the two, but it was the Sulina branch that commanded attention 163 years ago, when the European Commission of the Danube (ECD) was created to solve the problem of how to make the river navigable for deep-water shipping. With the end of the Crimean War, Britain and France seized the opportunity to break the Russian and Turkish stranglehold on the river, which, by one account, had turned Sulina ‘into an asylum for all the ruffians from Cape Matapan to Odessa’.

Under the Treaty of Paris of 1856, a hundred miles of the Delta were placed under international rule, and there they remained until Nazi Germany annexed Austria and asserted its control over the Danube, forcing Britain and France to withdraw. For three generations, Sulina and its environs operated as an autonomous state, with an independent foreign policy, police force and health and sanitary service, its own tax-gathering powers and, eventually, its own flag. So successful was the ECD that some historians consider the Crimean War, and not the Second World War, as the real midwife of the European Union as we have come to know it.

Sulina’s improbable transformation under the ECD from Danubian backwater into international entrepôt is captured in the pages of Europolis, a resonantly titled but now largely forgotten novel by the Romanian writer Eugeniu Botez, published in 1933, the year of his death. When the ECD moved in, Sulina was, according to the British civil engineer Sir Charles Hartley, like a postwar battleground, a ‘wild open seaboard, strewn with wrecks, the hulls and masts of which, sticking out of the submerged sandbanks, gave to the mariners the only guide to where the deepest channel was to be found’. On one winter’s night in 1855, twenty-four ships and sixty lighters were driven ashore, with the loss of over three hundred lives. And the Sulina branch of the river behind it was no less daunting: forty-five miles of twisting waterways, encumbered by drifting shoals of silt, draining as little as eight feet.

Hartley spent some fifty years in the Delta, observing the interplay of tides and sediments before launching a herculean attempt to reverse what nature had achieved over centuries. His solution, from a hydrological point of view, was forward-looking and, more to the point, cheap: natural scour. By narrowing the channel at Sulina and erecting elaborate harbour works, he forced the river to deposit its silt further out at sea, where it was more easily dispersed by the fast Black Sea currents.

By the turn of the century, Hartley’s walls, groynes, revetments and dogged dredging had transformed the Sulina branch into an almost straight, 34-mile canal with a minimum depth of twenty feet. Trade, mainly in Wallachian grain, expanded and Sulina flourished. The ECD, at its own expense, built houses, churches, schools and hospitals for the growing population, while a menu of tariffs introduced order and profit to what had historically been a disreputable neighbourhood.

While Hartley was the guiding light of Sulina’s prosperity, Botez was its main chronicler. Writing as Jean Bart, in honour of the 17th-century Flemish privateer, Botez was a pioneer of Romania’s marine genre of novel-writing and worked as a captain in the Sulina port administration in the early 1930s, when the gloss was already starting to fade. The title of Europolis, his last book, might suggest a futuristic dystopia with a Brussels accent, but, from Botez’s vantage point, it signified a different kind of modernity gone sour: colonialism.

Europolis tells the story of a Greek sailor, Nicola, who returns to Sulina after forty years in America, accompanied by his black adopted daughter, Evantia. As the city’s Greek community plots to exploit Nicola’s presumed unimaginable wealth, Evantia is pursued by every cavalier in town and is eventually impregnated by a notorious womaniser. Nicola dies in a scrape with the ECD river police, Evantia from consumption after she has been abandoned by her true love, a naval captain. So far, so simple.

But the narrative is played out against an intimate account of Sulina at its zenith, one of the very few available. Sulinian society was sharply divided between the blue-eyed expatriates of the ECD, Greek shippers, pilots and clerks, and the sailors who filled its bars by night. Largely out of sight are the Lipovani, who washed, cooked and cleaned in the incomers’ houses and took refuge in the seamen’s hospital when cholera came to call.

Botez is sceptical of the ECD’s civilising influence but is nevertheless in thrall to the rakish charm of this Black Sea Zanzibar. He describes the concerts, clubs and tennis tournaments designed to keep at bay the monotony within Sulina’s four electrified streets, beyond which lay the ‘Sahara’, a district named for the sand poured over it to suppress the vicious mosquitoes gathering around the town. It was in the Sahara, where light gave way to shadow, that the bar and the bordello reasserted their claims.

Although the book was written after Hartley’s death, his shade is clearly visible in Botez’s portrait of Sulina’s resident engineer, who has ‘a head like Bismarck’ and a ‘ruddy face streaked with bluish veins like a hydrological map’. Botez writes, ‘The resident rarely descended from his ivory tower, from where he directed the Commission’s immense machinery … and he never went into town.’

Sulina today still has the feel of a company town, thanks to its grid-like severity and the prominence of the two-storey houses built for its senior officials. The harbour, however, is empty, except for a Romanian tanker and boats offering trips into the wetlands. In the 1930s, as the tide retreated, it left Sulina high and dry. ‘Sulina’s gate was closing completely and forever,’ writes Botez in an epilogue. ‘The town is withdrawing, defeated in the battle with nature. Sulina is disappearing as a town.’ It is now further from the Black Sea’s open currents than in the early 19th century and the population has shrunk by half.

These days, the Tulcea ferry anchors near the former headquarters of the ECD – ‘like the residence of a colonial governor’ – where a bust of Sir Charles commemorates the man known as the ‘Father of the Danube’. It was erected in 2016, shortly before the tenth anniversary of Romania joining the EU. So far, the people of the Danube Delta have not been overawed by the new Europolitan regime. They blame the EU for raising the price of diesel and abolishing the cooperatives that once promised a minimum price for their fish. And, thanks to the EU’s strict sanitary requirements, the pike, carp and zander in which the Delta abounds are still only eaten within its confines.

Although Europolis has not been republished in English for many years, Botez’s meditation on the wisdom or otherwise of building one’s house on sand has proved rather more durable than Sulina’s brief prosperity.