Lake Toba & Samosir Island

The Toba caldera formed during a colossal eruption dated to about 74,000 years ago, which spread ash as far as South Asia. Afterwards magma pushed the lake floor upwards to form Samosir, which sediments show has risen by hundreds of metres. In July 2020 Toba Caldera was recognised as a UNESCO Global Geopark; after a 2023 warning (a so-called yellow card), it regained full green-card status in September 2025 following revalidation.

The lake shores are the homeland of the Toba Batak, one of several Batak groups of North Sumatra. Their villages are known for wooden houses on stilts with sweeping, saddle-shaped roofs and painted carvings. Samosir holds many of the most visited heritage sites, including the tomb of King Sidabutar at Tomok and the old village of Huta Siallagan at Ambarita, where stone seats recall the traditional council of village elders. Most Toba Batak today are Christian, and church singing is part of village life, while older customs remain alive in ceremonies, music and woven ulos cloth.

Life around the lake follows a farming and fishing rhythm, with rice fields and small farms on the slopes and small fishing boats on the water. The Toba Batak keep a strong sense of clan (marga) identity, and family ceremonies such as weddings and funerals can draw hundreds of relatives, with ulos cloth given as a sign of blessing. Christianity is the majority faith in most lakeside communities, so Sunday services are an important part of the week; Muslim travellers will find halal options more easily in Parapat and larger towns, and should ask before ordering in small village eateries, where pork dishes are common.