It has been protected as both a Place of Scenic Beauty and Natural Monument since 1934.

The canyon is named after the Chiiwa (乳岩), a large white limestone cliff with a height of 670 metres (2,200 ft) overlooking the river.

The cliff has many stalactites mainly composed of calcium carbonate from its overhangs, resembling breasts with milk.

The sides of the canyon are forested, and there are many caves in the area, the largest of which is called the "womb cave" and contains a statue of Kannon Bosatsu holding an infant.

Near the top of the mountain, there is a natural arch called "Tsutenbashi" or "Gokurakumon".