Indonesia consists of 17,508 islands, of which about 6,000 are inhabited. Indonesia straddles the equator, and the total land area of the country is 1,919,440 km². The largest islands in the archipelago are Java, Sumatra, Borneo (which is also shared with Brunei and Malaysia), New Guinea (shared with Papua New Guinea), and Sulawesi.

The highest mountain in Indonesia is Puncak Jaya in Papua, which reaches 4,884 metres (16,024 feet), and Lake Toba (on the island of Sumatra) is the largest lake, with a total area of 1,145 km² (442 sq mi). Indonesia’s largest rivers the Mahakam and Barito.

Indonesia is also known for its frequent volcanoes and earthquakes. There are around least 150 active volcanoes in the country including the famous Krakatoa and Tambora.