Indonesia, with over 18,000 counted islands, is by far the largest and most varied archipelago on Earth. (http://www.worldatlas.com)
There are 8,844 islands have been named according to estimates made by the government of Indonesia, with 922 of those permanently inhabited.
It consist of 5 big islands (from west to east on equator line) : Sumatera, Jawa (Java), Kalimantan (Borneo), Sulawesi (Celebes), and Papua. Each island consist of many provinces, and each province consist of many districts. Each province has their own culture and language. Now you see why every literatures say Indonesia is one of the most varies archipelago on Earth.
You really should do travelling to this place. Seas, mountains, lakes, rivers, highlands, lowlands, rainforests, savanas, waterfalls, caves, dunes, ancient things, you name it. Also, consider about floras and faunas, some are endemic and rare. And don’t forget the nice weather of tropical place.