The Rio Negro flows into Manaus from northwestern Amazonas, one of the least explored regions of South America. There’s virtually nothing in the way of tourist facilities in this direction, but it’s possible to make your way up the Rio Negro by boat from Manaus to Barcelos, from Barcelos to São Gabriel, and from there on to the virtually uncharted borders with Colombia and Venezuela. Alternatively, there are reasonably fast boats from Manaus every Friday, run by Asabranca, which call in at Barcelos (two days; R$100–200) on their way to São Gabriel (about five days up, three downriver; R$150–220). There are also daily flights to São Gabriel from Manaus, stopping off en route on alternate days at either Barcelos or Tefé on the Rio Solimões. To leave Brazil via these routes requires expedition-level planning and can take up to several weeks or longer, but it’s an exciting trip nonetheless.