What is the world's largest archipelago nation?

Indonesia, with something over 17,000 islands - the count varies because it depends what counts as an island and the surveys keep revising it - spread across more than 5,000 kilometres, which is roughly the width of the United States. About 6,000 are inhabited.

Holding it together required inventing a national language. The archipelago has over 700 living languages, and rather than impose Javanese, which the largest group spoke, the independence movement adopted a version of Malay - a trade language already used across the ports, and nobody's mother tongue in particular. Bahasa Indonesia was chosen precisely because it belonged to no one, and it worked.

It sits on the most geologically violent ground on Earth, at the meeting of several plates. Tambora in 1815 was the largest eruption in recorded history and caused the year without a summer on the other side of the world; Krakatoa in 1883 produced the loudest sound ever recorded; and the 2004 Boxing Day earthquake and tsunami killed over 220,000 people around the Indian Ocean. It is also one of the most biodiverse countries in the world, split by the Wallace Line - a boundary Alfred Russel Wallace identified between Asian and Australian fauna that runs between islands you can see across.