The stupendous roar of 275 different waterfalls crashing 80m (262ft) into the Rio Iguaçu means that even on the sleepiest, hottest afternoon, nature's relentless churning power will stir your heart here. The falls are actually divided between Brazil and Argentina. The best time to visit is between August and November.

To see the falls properly, you must visit both sides - Brazil gives the grand overview and Argentina the closer look. The Brazilian side has far fewer attractions than the Argentine side; and the costs are higher here if you want to arrange an under-the-falls boat trip. There are, however, some adventures unique to this side, including combination kayaking-hiking trips and rafting trips.

Five minutes' walk from the waterfalls' entrance is the worthwhile Parque das Aves, a five-hectare park where you can see some 800 different bird species. Pay in US dollars to avoid bad exchange rates.

The major attraction of the Parque Estadual do Caracol is the spectacular Cascata do Caracol, a 130m (426ft) waterfall which is incredibly beautiful in the morning sun. If you're feeling fit, you can walk down to the base of the waterfall (and back up) via 927 steps.

Ancient rock paintings, arches and caves grace Parque Nacional Sete Cidades, and just the highly unusual rock formations rising up from the surrounding flat, dry land make a memorable sight. Some people, educated scientists among them, claim the rocks are everything from seven ruined, 190 million-year-old cities to alien creations.

The 13km (9mi) walk to all seven cities takes two to three hours. Start your day early and bring snacks, water and protection from the unrelenting sun. Follow your tour with a swim in a pond or stunning waterfall (Dec-Jul only).

A remote floodplain forest, halfway between Manaus and the Peruvian frontier, is protected by the Mamirauá Sustainable Development Reserve. This 1.24 million hectare (3 million acre) reserve is part of the second-largest (57,000 sq km/22,008 sq mi) continuous block of protected tropical rainforest in the world.

Mamirauá combines nature conservation and scientific research with improved opportunities for the communities within the reserve.

Their excellent ecotourism program affords access to a pristine piece of towering primary rainforest, rivers and lakes absolutely teeming with life. Silence there will be the loudest you've ever heard, and wildlife-viewing is among the best in Amazonia.

Encontro das Águas (Meeting of the Waters) is where the dark violet Rio Negro meets the cafe-au-lait Rio Solimões, a few kilometres downstream from Manaus. The two flow side by side without mingling for several kilometers (owing to differences in speed, density and temperature), before finally combining to create the Amazon River.