The Republic of Indonesia is the largest archipelago in the world comprising 13,466 large and small tropical islands fringed with white sandy beaches, many still uninhabited and a number even still unnamed. Straddling the equator, situated between the continents of Asia and Australia and between the Pacific and the Indian Oceans, it is as wide as the United States from San Francisco to New York, equaling the distance between London and Moscow. Indonesia has a total population of more than 215 million people from more than 200 ethnic groups. The national language is Bahasa Indonesia.
Among the most well known islands are Sumatra, Java, Bali, Kalimantan (formerly Borneo), Sulawesi (formerly Celebes), the Maluku Islands (or better known as Moluccas, the original Spice Islands) and Papua. Then, there is Bali “the world’s best island resort” with its enchanting culture, beaches, dynamic dances and music. But Indonesia still has many unexplored islands with grand mountain.
Source : http://www.indonesia.travel/en/travel-guidance