The world famous crater lake of Danau (Lake) Toba is the third biggest tourist destination of Indonesia. The island in the huge lake, Pulau Samosir, attracts many tourists. Lake Toba is the largest lake in Southeast Asia, once created by an enormous eruption less than 100.000 years ago. The eruption was approximately 8.000 times more powerful than the eruption of Mount St. Helen in 1981. Ashes in the stratosphere circled around the earth for years and changed the climate. As things began to settle another volcanic eruption happened about 25.000 years later and built up a secondary volcano inside the caldera. The cone of that volcano collapsed and formed the island Samosir while the crater of the first eruption filled with water, what to become Danau Toba.

The lake covers approximately 1.265 square km excluding Samosir and is 90 km long. The depth is in on average 450m and up to 900m in some places. The lake is situated at an altitude of 906 m above sea level. The steep coastline interspersed with small valleys creates fantastic scenery and isolated areas. The deepest end and the highest mountains are at its northeastern end. The Dutchman H.N. van der Tuuk was the first European who saw and reported about the lake, in 1847.

There are of course legends on how Lake Toba was formed. The following is a Batak Toba legend: Once upon a time there was a man living in the area of the present day Danau Toba. No one knew when or from where he came. He lived in a simple hut in a farming area. He had a garden and did some fishing. One day he caught a big fish in his trap. It was the biggest catch ever in his life. Back home the fish turned into a beautiful princess decorated with jewels. He fell in love with her and proposed to her. She nodded romantically, however, the princess had one condition. The man had to promise never to tell anyone that she had been a fish. If he would, there would be a disaster. They married and got a daughter and lived happily. The daughter always brought lunch to her father out in the fields. The girl was however very greedy and one day she ate all her father's lunch. Her father got angry and scolded: "You damned daughter of a fish!" The princess started to cry when she heard what her husband had said. She told her daughter to go to the hills, as there would be a disaster. When the daughter had left for safety the princess prayed. Soon there was an earthquake, rain started to fall and springs appeared everywhere. The whole area got flooded and became Lake Toba. The princess turned into a fish again and the father became the island of Samosir.

According to a Simalungun legend, told in Pematang Raya, there was once a mountain called Gunung Tuhaweoba in the area where Lake Toba is now. (Tuhaweoba is also the name of a kind of pepper). A long time ago the mountain exploded, Lake Toba was formed and the people were divided. Those on the western side of the lake became the Batak Toba and on the eastern side Batak Simalungun. The word Tuhaweoba changed over time to Tuba and later to Toba.

The traditional Batak canoe, the solu, was 10-15m long. All had the same width. The canoes of the chiefs were decorated with carvings. The captain, the Chief, sat in front and gave orders. The solu had its own spirit and when a new canoe was built offerings were made for both the canoe spirit and to Boru Saniang Naga, the Goddess of the water. Bataks feared her as disasters could easily happen when she was angry.

Three years ago Lake Toba reached its lowest water level ever, which caused problems, for example for tourism. The level had then fallen several meters and the lake was a rather depressing sight for people who had seen it before. The reasons for the falling water level were deforestation and over consumption of water by a pulp factory and a hydroelectric power plant near Porsea. The companies consumed more water than the capacity of Lake Toba allowed. After strong and sometimes violent protests from the local communities, the pulp factory, Indorayon, was closed down. The protests were based on many different interests and concerns, amongst others of course environmental concern. The water level is however, also controlled by the big dams of PT Inalum. Since the closure of Indorayon, the water level in Lake Toba has reached its normal level and the lake has regained its original beauty.