Lake Toba 

Lake Toba is an immense volcanic lake covering an area of 1,707 sq km (1,000 sq km bigger than Singapore) with an island in the center. Formed by a gigantic volcanic eruption some 70,000 years ago, it is probably the largest resurgent caldera on Earth.

Most visitors fly to Medan and then travel by land to Parapat, the town by Lake Toba. Parapat is about 4 hours by car from Medan (4-6 hours by public bus). You can get from Medan airport to Lake Toba entirely by public transport if you wish. First, you must go from the airport to Amplas bus terminal. Walk through the car park and go out the main car exit of the airport, cross the road and turn left after the petrol station, and then turn right (about a ten-fifteen min walk altogether). There, you can catch a yellow public bus, number 64, to Amplas Terminal for Rp 3,000. From Amplas terminal, you can get a public bus to Parapat for Rp 22,000. So you can get from Medan airport to Parapat for a total of Rp 25,000 (September 2012), and then get a ferry out to Samosir island for Rp 7,000/person. The boat drops you at your hotel.

other way, From Medan Polonia airport you can fly directly to Silangit with Susi Air daily . Flights take approximately 30 minutes and is a much better and safer way than the road trip. 2012 September the flight costs 380,000 IDR $38 USD one way. Transportation options from Silangit airport are limited; it is a good idea to pre-arrange a driver to be waiting; From Silangit Airport to Parapat take 2 hours drive. To Silangit airport from Parapat there are many transport providers available around the ferry terminal area. Costs to / from Silangit and Parapat should cost around 300,000 IDR each way per vehicle.

Parapat is connected to Tomok and Tuk Tuk on the Samosir Island by boat/ferry that run every 1-2 hr, the last one at 6PM (Rp 7,000). The place to catch the ferry to Tuk Tuk is called "Tiga Raja" harbour/jetty. Some ferry's owner are tourist hunter and will overcharge you for Rp 20-30,000 for the same trip to Samosir Island. In my opinion try to observe the ferry with wooden bench inside and light green colored ferry. Those are the ferries that charge Rp 7,000 and the locals take to cross over. Self proclaimed 'Tourist Hunters' may befriend you on the boat but are harmless and often helpful. Tuk Tuk is the main town to stay on Samosir. Use the boat service not the large ferry, they will drop you directly at your Tuk Tuk resort.

There are also two other harbour in Samosir, they are: Nainggolan (1 hour drive from Tomok) connected Muara, the ferry runs every Sunday, Monday, Wednesday, and Friday, and the other located in Simanindo (30 min drive) connected to Tigaras which runs daily until 6PM.