Let KAYAK do the searching
Based on KAYAK hotel searches, the most popular destination is Medan (91% of total searches to North Sumatra). The next most popular destinations are Parapat (3%) and Berastagi (3%). Searches for hotels in Tongging (3%) are also popular.
KAYAK users have found double rooms in North Sumatra for as cheap as S$ 9 (Parapat) in the last 3 days. The average price is S$ 45.