Malabo is the capital of Equatorial Guinea and the country's largest city. It is located on the island of Bioko, in the Gulf of Guinea. The city has a population of approximately 622,000, and is the principal city of the province of Bioko Norte. Malabo is situated on the north coast of Bioko, which is the result of sediment deposited by the Bioko and Annobon rivers. The island of Bioko is the result of volcanic activity, and the most recent eruption occurred in 1957. The city is in a tropical rainforest which is home to a great diversity of wildlife, including the drill, the world's largest primate.