BUILDING CHALLENGES: The city is surrounded in all directions by dense Brazilian rain forest
Frans Lanting/National Geographic Stock

It also happens to be a most unlikely place to find a guy from the Great White North. A city that swelters in the humidity of a ­superheated equatorial climate and bustles with irrepressible Latin energy, Manaus is a long way from the cool, collected confines of Canada. But here I am for more than a week to explore this curious city — snapping caiman and all.

When you look at Manaus on a map, it appears to be a dot surrounded by a whole lot of blank space. But the blue lines that flow around it? Those are key. In a place without roads, where both trade and human transportation move almost exclusively by boat, this city is truly the crossroads of the Amazon.

Here, the Rio Negro — the largest black-water river in the world — meets the Rio Solimões, combining to form the world’s greatest waterway, the Amazon River. Joined by Patrick Reynolds, a fish and wildlife biologist originally from Arkansas who has lived in Manaus for the past four years, running an eco-tour company with his Brazilian wife, Gloria, I start my adventure by heading down to the water. We board a private boat chartered by Reynolds and roar out into the middle of the Negro. “This river — here it’s a road,” Reynolds tells me in a distinctly Southern twang, nodding to a bunch of three-tier wooden riverboats clustered at docks all along the shore. “Those take people and cargo all over the place.”
MEETING OF THE WATERS: The Rio Negro, the world's largest black-water river, combines with the Rio Solimões to form the Amazon River. The two rivers flow without mixing for more than three miles.
John Warburton Lee/SuperStock

He explains that despite Manaus’ remote jungle location, its position on these deep, wide, easily navigable rivers makes it a prime spot for refining South America’s oil, as well as a free-trade zone where tech giants like Samsung and Sony can manufacture their electronics. Pointing to a giant ship up ahead, Reynolds says, “Ocean liners steam all the way up here from the sea.” A few moments later, he adds that we will be arriving at the intersection of the Negro and the Solimões, and he tries to prepare me for that moment. “It’s truly something to behold. … I don’t think you can see anything of that magnitude anywhere else on Earth.”

And true to Reynolds’ billing, when we reach the meeting of the waters, I can’t quite believe my eyes. While the Rio Negro looks like a cup of coffee served black, the Rio ­Solimões, which flows in from the far side of a flat headland, looks as if it has been loaded up with two creams and two sugars (what we’d call a “double-double” in Canada). The two are divided by a distinct line — not mixing at all — and they stay like that, flowing side by side but separate, for more than three miles.

As we motor toward the Solimões, Reynolds tells me to put my hand in the river. In spite of my reservations — mainly because we are sharing these waters with piranha, caiman and weird (and to me, scary-looking)­ pink dolphins — I comply. As we cross ­between the two, the water flowing through my fingers goes from relatively warm to rather cool, and the change happens immediately after we pass the line. “The Solimões flows from melted snow, 18,000 feet up in the Andes, and the Negro doesn’t,” Reynolds explains, adding that differing levels of sediment and velocity (the Solimões flows at a rate more than twice as fast as the Negro) are also behind the stark division. Doubling back, we straddle the line and pause for a few minutes. Reynolds gestures in different directions. “If you go that way, you’ll get to Colombia, and over there is Peru,” he says. Then, hiking his thumb over his shoulder, “And down there about 1,000 miles, that’s the Atlantic.”