Samosir Island was artificially turned into an island. Originally a peninsula, it was transformed into an island when a canal was cut through the isthmus connecting it to the crater wall that surrounds Lake Toba.
The 630 sq. km island in the middle of Lake Toba can be reached half an hour by boat from Parapat. Boats usually leave from Samosir Island to Prapat and back with passengers. Boats could leave in either direction at anytime.