The v-shaped valley along Jinno-gawa River, a branch of Totsu-kawa River, is particularly well developed among the rivers in the Kii Mountains, the distance between ridge lines on both sides is 10 kilometers, the depth is more than 500 meters, the vertical drop from Kawatsu which is a joint of Jinno-gawa River and the main stream of Totsu-kawa River to the divide is more than 1,000, however it does not have great flections.
特に十津川支流の神納川のV字谷は、紀伊山地の中でも発達が著しいもので両側の稜線間の距離は10キロメートル、深さは500メートル以上、神納川と十津川本流との合流点である川津から分水嶺までの標高差は1000メートル以上に及ぶが蛇行はさほどではない。