Brazil is the world's fifth-largest country, occupying almost half the South American continent and bordering every country on it except Chile and Ecuador. Much of Brazil is scarcely populated, although some regions with previously low population densities, such as the Amazon, are being rapidly settled, logged and depleted.

Brazil can be divided into four major geographic regions. The long, narrow Atlantic seaboard has coastal ranges between the Rio Grande do Sul and Bahia, but is flatter north of Bahia. The large highlands - called the Planalto Brasileiro, or central plateau - which extend over most of Brazil's interior south of the Amazon Basin are punctuated by several small mountain ranges and sliced by several large rivers.

There are also two great depressions: the Parana-Paragui basin in the south, which is characterized by open forest, low woods and scrubland; and the huge, densely forested Amazon Basin in the north. The Amazon, 6275km (3890mi) long, is the world's largest river. It carries more water to the sea than any other river and the Amazon forest contains 30% of the world's remaining forest.

The richness and diversity of Brazil's fauna - much of which is endemic - is astounding, and the country ranks first in the world for numbers of species of mammals, freshwater fish and plants; second for amphibians, third for bird species; and fifth for species of reptiles. Despite its natural riches, Brazil is renowned for the destruction of its environment. All of Brazil's major ecosystems are threatened, not just the well-known Amazonia. Many species are under threat because of the continued depletion of rainforests, desertification in the northeast, poaching in the Pantanal region and coastal pollution.

Most of the country has noticeable seasonal variations in rain, temperature and humidity, but only the south of Brazil has large seasonal changes. The Brazilian winter is from June to August, with the coldest southern states receiving average winter temperatures of between 13ºC and 18ºC (55ºF and 64ºF).

In summer (December to February), Rio is hot and humid, with temperatures in the high 30ºsC (80ºsF) common; the rest of the year, temperatures usually hover around 25ºC (77ºF). The northeast coast gets as hot as Rio in the summer but tropical breezes make it less humid and stifling.