Sun Moon Lake is in Nantou County in central Taiwan, roughly 2.5 hours from Taipei by bus. The fastest approach from Taipei is the High Speed Rail to Taichung, then a direct Nantou Bus (Route 6670) from the Taichung HSR station to Sun Moon Lake — this takes about an hour and is reliable and convenient. Buses also run from Taichung City bus station.
From Taipei, direct buses to Sun Moon Lake are also available but take around 3.5 hours. There is no rail connection to the lake itself. Driving from Taichung takes about an hour; the roads through the mountains are scenic but winding. Once at the lake, the boat ferries and cycling path are the practical ways to get around — a car is not especially useful.