Recently I drove northeast from Wushe (霧社) in Nantou County, past Qingjing Farm (清境農場) and over Hehuanshan (合歡山). This stretch of road is the highest in Taiwan, cresting at 3,275m; Hehuanshan's peak is 3,416m above sea level.
The section shown here isn't the very top but gives you a good idea of the scenery. On weekdays there's usually little traffic; at weekends and whenever there's snow, you can expect crowds of people and vehicles. Hehuanshan is inside Taroko National Park. If you'd rather not drive, you can see this road by taking one of the buses which link Puli (埔里) with Lishan (梨山).