The larger of these is Bioko, formerly known as Fernando Po.
It lies 25 miles (40 kilometers) off the coast of Cameroon, across a bay of the Gulf of Guinea known as the Bight of Biafra, to the northwest of the continental portion of the country.
In Río Muni, coastal plains rise to hills, and then to plateaus farther inland.
Bioko has three extinct volcanic cones, which contain several crater lakes. Río Muni is mainly tropical rain forest and is home to a variety of animals, including gorillas, chimpanzees, monkeys, leopards, elephants, and crocodiles.
Today the country is still attempting to rebuild and to establish a degree of political and economic stability.
However, its record continues to be marred by human rights abuses.
Bioko was important as a slave trade center, thanks to flourishing cocoa plantations there, and was one of Spain's most profitable territories in Africa.
However, the island was administered by the English from 1827 until 1858, at which point the Spanish takeover became official.
The country's total area is 10,830 square miles (28,050 square kilometers; slightly smaller than the state of Maryland).
This includes the mainland portion (Río Muni), as well as three coastal islets (Corisco, Elobey Grande, and Elobey Chico) and two islands (Bioko and Annobóon).