JIGOKUDANI YAEN-KOEN|Welcome , Japanese Monkey to the world The Jigokudani Yaen-koen (altitude 850 meters) is located in the Valley of Yokoyu River sourced from Shiga-Kogen of the Joshinetsu-Kogen National Park in northern part of Nagano prefecture Because of the very steep cliffs and the steam coming off the springs in everywhere, ancient people called this valley ‘Jigokudani (Hell valley)’ Also it is buried in snow almost one third of the year