Lake Toba is on most itineraries of travellers going to Sumatra. The lake is set in the caldera of a giant volcano and it's the largest lake of South East Asia. Right in the middle there is an island Pulau Samosir, which is about the size of Singapore. The climate is pleasant and the setting is cool as well. This makes Lake Toba a favourite get away for people living in less-than-appealing city of Medan. Medan is less than 200 km away and many buses make the trip every day. The unique thing from Lake Toba is about a small lake within the lake itself. The lake so called Danau Sidohoni [Lake Sidohoni] and situated in Pulau Samosir [Samosir island]. And Pulau Samosir itself is connected to Sumatra mainland by a bridge named Jembatan Diponggol, situated at Pangururan.
The main concentration for tourists [for spots and accommodation] are on Tuk Tuk and Ambarita. Tuk Tuk is about the old cemetery of the King Sidabutar, stone chairs and Ambarita is place to stay whenever you find Tuk Tuk quite hectic.The enroute from Medan as the capital city of north Sumatra as follows: Medan, Pematangsiantar, Parapat and Lake Toba. Take a ferry to visit Pulau Samosir, takes about 30 minutes. [from world66.com by Ukirsari and Srdjan]