Why go? Unlike the other islands here, Samosir is not all at sea. This is the world’s largest island within an island, a colossal volcanic lump the size of Singapore stranded in Sumatra’s Lake Toba – itself the largest volcanic lake in the world. The highest point of Samosir looms around 800m above lake level (a worthwhile hike for the views). Down at the shore, there’s geothermally warmed swimming and boat trips galore. Most interesting, though, is delving into the local culture – Samosir is the heartland of the laidback and welcoming Toba Batak people. Visit Batak villages (Simarmata is one of the best preserved), watch a traditional Batak dance and pay your respects at the tomb of King Sidabutar, the Batak ruler who adopted Christianity in the 19th century.

When to go: May-September is the driest period.

How to go: The closest airport to Parapat, the harbour on the eastern side of Lake Toba, is Medan (4-5hrs by bus). Ferries leave from Parapat for Tuk Tuk (1hr) on Samosir.