Lake Toba (Danau Toba) is the largest lake in South East Asia and is located in Sumatra, Indonesia. The island in the middle - Pulau Samosir - was joined to the caldera wall by a narrow isthmus, which was cut through to enable boats to pass; a road bridge crosses the cutting. You get a ferry from Parapat to Pulau Samosir Island.
Lake Toba used to be popular tourist destination but now not many tourist come, which means many services, no crowds, cheap prices and friendly locals grateful for your business.