Meeting of the Waters, Manaus

Just outside Manaus, the dark, warm Rio Negro meets the cooler, sandy-coloured Rio Solimões, and the two rivers run side by side without mixing for about 6 km before becoming the Amazon. Boat trips from Manaus take you out to see the line between them; you can put your hand in each side to feel the difference.

Most tours combine it with a jungle walk, a floating village and the giant Victoria water lilies. For a deeper experience of the Amazon rainforest, home to a third of the world's species, stay a few nights at a jungle lodge up one of the rivers, with canoe trips, caiman spotting at night and pink river dolphins.