There are total number of 17,508 islands of which about 6000 are inhabited. Straddling equator, the archipelago is on a crossroads between two oceans, the Pacific and the Indian Ocean, and bridges two continents, Asia and Australia.
The territory of the Republic of Indonesia stretches from 6°08' N latitude to 11°15' S latitude, and from 94°45' E to 141°05' E longitude. Total Area of Indonesia is 1,919,440 sq km (Land Area: 1,826,440 sq km; Water Area: 93,000 sq km).
The five main islands are: Sumatra (473,606 sq. km); the most fertile and densely populated islands, Java/Madura (132,107 sq. km); Kalimantan, which comprises two-thirds of the island of Borneo (539,460 sq km); Sulawesi (189,216 sq km); and Irian Jaya (421,981 sq km), which is part of the world's second largest island, New Guinea. Indonesia's other islands are smaller in size.
The country is predominantly mountainous with some 400 volcanoes, of which 100 are active. The highest mountain is the perpetually snow-capped Mandala Top (15,300 feet) in the Jaya Wijaya mountain range of Irian Jaya.
Many rivers flow throughout the country. They serve as useful transportation routes on certain islands, for example, the Musi, Batanghari, Indragiri and Kampar rivers in Sumatra; the Kapuas, Barito, Mahakam and Rejang rivers in Kalimantan; and the Memberamo and Digul rivers in Irian Jaya.