Ruisui sits in the middle of the East Rift Valley, a long, narrow trough between the Central Mountain Range to the west and the Coastal Mountain Range to the east, and it is also right on the Tropic of Cancer. A monument by the highway marks the line, and it is a popular photo stop. The valley here is flat and fertile, with rice paddies, pineapple and pomelo orchards, and tea gardens on the terraces above, and the mountains on either side rise steeply into cloud.
The valley exists because of plate tectonics. The Coastal Mountain Range is part of a volcanic arc that has been pushed against Taiwan by the Philippine Sea plate, and the rift valley marks the seam between the two. Earthquakes are frequent, and the land is still moving: some of the roads and bridges show signs of being shifted over time. The rivers that run through the valley, including the Xiuguluan, which cuts through the Coastal Range to the sea, are wide and gravelly, and the Xiuguluan is Taiwan's best-known river for rafting, with trips starting near Ruisui.
Ruisui is known for its hot springs, which are unusual for their iron-rich, rust-coloured water, and the town has several bathhouses and inns built around them. The area is also home to Amis communities, Taiwan's largest indigenous group, whose harvest festivals in summer are a major event. Nearby tea plateaus grow a local tea that is worth trying, and the cattle ranch on the hills above the town sells milk and dairy products.
The riding along Highway 9 through the valley is easy and pleasant: long straights, gentle curves, little traffic outside of holidays, and mountains on both sides. Side roads into the hills offer more challenge, and the road over the Coastal Range to the sea is particularly beautiful. Ruisui has fuel, food and beds, and an hour in a hot-spring bath halfway along Highway 9 does wonders for a stiff back. Hualien, about sixty kilometres north, is the nearest large city. The valley can be very hot in summer, and afternoon thunderstorms are common, so start early and carry rain gear.