What are the features that make Samosir Island so interesting?

Samosir Island has the distinction of being the largest island within an island. It is a volcanic island in Lake Toba which is a lake in the island of Sumatra.

 The island was born as a result of two dramatic prehistoric volcanic events. A gigantic volcanic explosion first created a huge crater that became Lake Toba. Samosir was formed by a new volcano cone pushing up through the existing Lake Toba volcanic crater. It was actually a peninsula jutting into the lake.

 But in 1906, the Dutch dug a canal across the connecting strip of land and Samosir became an island. Samosir is about the size of Singapore, and is the heart of the culture of the Toba tribes of North Sumatra.