Manaus may not rank at the top of most Brazil must-see lists in the way that Rio de Janeiro or São Paulo do, but this major port city has the appeal of a pretty historic center - complete with 19th-century architecture - and its proximity to the Amazon makes it a popular jumping-off point for exploring the nearby river and forest. Additionally, the city is an excellent destination for shopping - even Brazilians from other cities make trips to Manaus to buy what the city has to offer.
Harvesting and exporting rubber in the late 1800s brought immense wealth to the so-called “rubber barons” of Manaus, and many of the city's attractions date from that era. The primary must-see attraction in the city center is the Teatro Amazonas, the city’s opera house, which faces the lovely San Sebastian Square. Another 19th-century building on the square is the Church of San Sebastian, and the nearby Mercado Municipal is modeled after the legendary Les Halles public market in Paris.
Manaus sits at the junction of two big rivers in northern Brazil, the Rio Negro and the Rio Solimões, which combine to become the mighty Amazon. The meeting of these two rivers is actually an attraction in and of itself. Each river is a different temperature, a different color and running at a different speed, so rather than blending seamlessly in the middle they actually run alongside one another for about four miles - two bodies of water with a clear border between them.
While Manaus itself lies quite a distance inland from the Brazilian coast, the rivers provide several beaches that are popular with locals and can make a nice day-trip getaway from the bustle of the city. River beaches in Manaus are at their peak when the rivers are lowest, roughly from August through December - this is when the beaches themselves are larger, thanks to the water level receding.
Ponta Negra beach, about eight miles from downtown, is arguably the most popular local beach, while Praia da Lua beach just beyond it is a bit more secluded and quiet. You can reach Ponta Negra by bus or taxi; to get to Praia da Lua, you will need to take another bus to the marina, from which you can catch a boat to this more remote beach. Plan to get back to Ponta Negra by the evening, since the area is also famous for its night life.
To get a deeper understanding of the Amazonas region, you can spend a bit of time in the museums of Manaus. There are a couple of museums in Manaus dedicated to the region's indigenous populations - the Museu do Índio and Museu Amazônico - and a Natural Science Museum (outside the city center) with an impressive 200-ton aquarium and collection of stuffed fish and insect specimens found in the area. This is one way to check out the Amazon wildlife without heading into the jungle.
Spend the remainder of your last day scouring the busy shopping streets and Mercado Municipal in Manaus, picking up any additional souvenirs you want to bring home as well as any electronics that catch your eye (the city is home to several electronics manufacturers).