The last section of Hwy 24 is a gorgeous winding highway that leads you deep into the mountains. Not for the fainthearted, some parts of the road run along very steep cliffs. Do check the road conditions before setting off, as the area is inaccessible during heavy rains. You have to register at the police station (at the KM26.8 mark) before entering the Wutai area.
This section of the road, between Sandimen and Wutai (霧台; Wùtái), is 18km long and the altitude changes from 100m to above 1000m. Expect head-spinning views of the river, valleys, waterfalls, cliffs and indigenous villages. Wutai (after the Km39 mark) is an attractive Rukai settlement, with an unusual Catholic church and traditional slate-walled houses.
From Wutai, you can continue the last 8km to the abandoned village of Ali, or head back and make a detour to Dewen (德文; Déwén), a pretty coffee-growing village sitting 800m to 1200m above sea level. To get to Dewen, switch to County Rd 31 (northbound) before you reach the police station (if you're going downhill). From this turnoff, it's a 6km drive to the village.