Lake Toba rests in a giant volcanic caldera. A caldera is formed when land collapses following a volcanic eruption, and the volcanic eruption which took place 70,000 years ago in the place where the lake is now is considered to be the largest volcanic eruption to take place on Earth in the last 25 million years. It was so big, it is considered to be a super volcano, and had such a destructive impact on the Earth’s climate that it is thought to have caused the last ice age.
Fortunately, Lake Toba is slightly more benign today. The lake is 100 kilometres long and 30 kilometres wide, and 505 metres (1,666 ft) at its deepest point.
Lake Toba used to be more popular with visitors than it is today, and the reason for the declining numbers can probably be attributed to the poor infrastructure, particularly the roads which lead from the city of Medan, which, these days see a lot of heavy vehicle traffic yet are poorly maintained.
If you do make the effort to visit, then the trip is certainly worthwhile.
The drive from Medan to Parapat, a town on the edge of Lake Toba can take anywhere from four to six hours, depending on traffic and the state of the roads. Parapat is a nice little town with reasonable accommodation, good food and water-based activities, however, you would really be wanting to visiting Samosir island, which is actually on the lake.
Although there is a very poor road and bridge connecting the island with the mainland, the best way to go is by water. There are regular ferries, or you can hire a boat for a very reasonable price. The ferries take one hour to make the crossing, but the speed boats are much quicker. You will find touts trying to get you onto the boats. Do not pay in advance, negotiate a price and pay when you arrive.
Samosir island is the cultural centre of Batak tribe who are mostly Christians these days. Most visitors stay on the peninsula of Tuk Tuk on Samosir, and it is a good place to stay several days. To entertain yourself on Samosir head out to discover the island, such as visiting traditional Batak villages, swimming in the lake and going to the hot springs in Pangururan.
The easiest way to get around Samosir is by boat, but you can also hire motorbikes, but remember the roads are bad, and road rules seem to be almost non-existent.
Although there are some seriously hot springs on the island, the waters of the lake are also warmed due to them being in a geothermally active area, but they are tolerable and quite comfortable.
Lake Toba is a very interesting place to visit, but, at this stage, it is for adventurers. Nevertheless, if you don’t wish to travel independently, it is easy to pick up 3 and 4 day excursions from Medan.