Parapat is a small town on the edge of Lake Toba.
From Medan there is a local bus (no air-con) about every hour for 32,000 rupiah (Feb 2014) if you pay on the bus. The journey takes 4-6 hours, depending on the traffic condition.
There are also several mini buses plying for IDR60,000 per person. If you are carrying heavy luggage, you might be asked to buy one extra ticket for the luggage.
Sibisa Airport is the closest airport to Prapat, however the short runway only for very light aircraft. Silangit Airport is close to Balige, may be accessed by Wings Air from Batam.
Asahan River, especially around the Tangga village in the district of Bandar Pulau, has a speed of 120m/s with grade IV-V+ with an average 5m depth and is very challenging.
Buses from Medan to Padang, Bukkittingi and Jakarta go through Parapat. Bus to Padang costs 240,000 IDR and leaves at 4:30 PM from ALS Bus Station. It reaches Bukkittingi at 8 in the next morning and at Padang at 10 AM. Book ahead of time or risk being crammed in the back without a seat for the same price.