Rio San Juan, Nicaragua

Lancha

The conquistadors explored it in the 16th century. English pirates sailed up it in the 17th century. Epic battles Lanchatook place on its shores. Soldiers killed by tropical diseases were fed to the flesh-eating sharks of its dark waters. In the 19th century, gold-diggers rushed up it towards California. In the early 20th it nearly became an international inter-ocean canal in place of Panama. Really, the heavy currents of history flow in Nicaragua's Rio San Juan.

This powerful river carries the waters of Lake Nicaragua, Central America's largest body of freshwater, 192km eastward to the Caribbean. The only "road" through this remote rural area, it runs between vast reserves of thick tropical rainforest on its left bank and isolated farming communities on its right bank, which is in fact Costa Rican. The full journey downriver takes twelve hours. Always one for an off-the-beaten-path expedition, I puttered down the river over the course of several days, soaking up the tranquil atmosphere.

I caught my first glimpse of the Rio San Juan at daybreak, as my ferry reached the fishing town of San Carlos after a fourteen-hour lake crossing. In the ethereal dawn light, the water and the sky would have merged their twin expanses of blue-grey, had they not been divided by the dark, mist-covered shoreline. "The threshold of an adventure!" I exclaimed, excited.

The next day, I embarked on a lancha, a long and impossibly narrow wooden motorboat that ferries passengers, sacks of rice and even sometimes a shipment of cows from one settlement to the next. We glided in the wake of Benalcazar, who reconnoitered the river for Cortés in 1525 during the Spanish conquest.

Castillo

Indeed, the conquistador had figured out the strategic importance of a waterway almost linking the two oceans (the western edge of the lake is just a few hours from the Pacific). But so had English filibusters, among which the infamous Henry Morgan. In the 17th century, he and other pirates repeatedly sailed from the West Indies right up to Granada, sacking what was one of the Spanish empire's richest cities.

In response, the Spanish fortified the Rio San Juan. Only one fort still stands intact, the 1675 Fortaleza de la Inmaculada Concepcion, whose dark mass looms above the town of El Castillo. I spent a happy morning at the museum of the fort trying to picture myself as Rafaela Herrera, who fired cannons from that very spot in 1762.

Since her father, the commander of the fort, had died just as English buccaneers were about to attack, she promptly proclaimed herself head of the garrison and successfully led the defense of the fort – she was 19! Later, an English fleet under the orders of Horatio Nelson did take the fort in 1780, in one of the last battles between England and Spain, but the conquerers were quickly decimated by a cohort of tropical diseases.

Scratching my own mosquito bites, I cursed the surrounding jungle and set off for the mouth of the river, another eight hours away. Once the boat had navigated the frothing rapids just beneath El Castillo, the ride was smooth. En route, we stopped in several tiny communities, really just a handful of thatched wooden farmhouses sheltered by banana trees. Half-naked kids and their dogs watched the farmers in rubber boots and cowboy hats clamber off. It was probably the most dramatic event of their week.

Carlos

The end of the ride is San Juan de Nicaragua, a small collection of clapboard houses connected by footpaths near the mouth of the river. Its glory days (as Greytown) started during the gold rush of 1848, when an enterprising American set up the Ruta del Transito, a route which ferried thousands of gold-seekers from New Orleans to San Francisco by way of Nicaragua's Rio San Juan, avoiding the direct but dangerous overland journey – until the continental railway was inaugurated.

The river's last hopes to become an international shipping lane were destroyed when Panama was chosen over Nicaragua for an inter-ocean canal in 1903, and the town turned into a backwater. In the 1980's it was razed by the Contras and flattened by a hurricane, then rebuilt a few miles away.

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