Takachiho Gorge is the town's defining sight. The Gokase River cuts through dark volcanic rock, and the 17-metre Minai Waterfall drops straight into the narrow channel. From the path above you get the shape of the ravine; from a rental boat, when they are running, the cliffs feel much taller.
The riverside path is short, but it packs in the best views: rock formations, bridges, the waterfall, and the tightest part of the gorge. Come early if you want the place before tour groups and boat queues take over.