The lake and island were formed after the eruption of the Toba supervolcano some 75,000 years ago.

The island was historically linked to the mainland of Sumatra on its western part by a narrow isthmus connecting the town of Pangururan on Samosir and Tele on mainland Sumatra, but it was split by the Tano Ponggol Canal and bridge in 1906, which was widened in 2019.

One of the most important objects on the island is a Lutheran church, and opposite it is a huge hill.

Samosir is a popular tourist destination due to its exotic history and the vistas it offers.

A car ferry leaves the mainland from Ajibata and lands in the small town of Tomok, about a 10-minute drive from Tuktuk until 9 pm.