Lake Toba, Samosir, Berastagi and Medan (North Sumatra)

The province of North Sumatra stretches across the island of Sumatra between the Indian Ocean and the Strait Malacca. It borders Aceh province on the northwest and Riau and West Sumatra provinces on the southeast. It has an area of 70787 km². The province contains a broad, low plain along the Strait of Malacca coast. In the south and west, the land rises to the mountain range that runs the length of Sumatra; the mountains here are dominated by Lake Toba, formed from the caldera of an ancient volcano.

Medan is the capital of the province of North Sumatra, Indonesia. Located in the northern part of the province along the coast, Medan is the third largest city in Indonesia. The city is bordered by Deli Serdang Regency to the east, south, and west, and the Strait of Malacca to the north.

Lake Toba (Indonesian: Danau Toba) is a lake and supervolcano, 100 km long and 30 km wide, and 505 m. (1,666 ft.) at its deepest point, in the middle of the northern part of the Indonesian island of Sumatra with a surface elevation of about 900 m (3,000 feet). It is the largest volcanic lake in the world. In addition, it is the site of the 75,000-year-old supervolcanic eruption, the largest in the last 25 million years; where it staged a massive climate-changing event that scientists believe might have wiped out much of humanity.

Samosir, or Pulau Samosir, is a large volcanic island in Lake Toba. Lake Toba is located in the north of the island of Sumatra in Indonesia.
The lake and island were formed after the eruption of a super volcano some 75 000 years ago. The island was originally connected to the surrounding caldera wall by a small isthmus, which was cut through to aid navigation.
At 630km², Samosir is also notable as being the largest island within an island, and the fifth largest lake island in the world.
Samosir is a popular tourist destination due to the fantastic vistas it offers. The tourist resorts are concentrated in the Tuktuk area. The island is the centre of the Batak culture and many of this people's artifacts remain on the island.

Source: Wikipedia Travel