Dakigaeri Valley is known as the Yabakei of Tohoku, and is a beautiful spot famous for its virgin forests on both banks, the waterfalls hanging over the cliffs, and the distinctive blue river.
There is a walking trail where you can easily see the strange rocks, rapids, and waterfalls of all sizes. The view from the suspension bridge "Kami no Iwabashi" that catches your eye when you reach the valley is amazing.
Dakigaeri Valley leaflet (PDF data)