The Jigokudani Valley in Japan's Joshinetsu-Kogen National Park is a high altitude, snow-covered landscape of cliffs and chasms that holds a surprising secret: naturally occurring hot springs that bubble with subterranean heat and fill the air with steam. However, we humans aren't the only primates who have discovered the hot springs. In the early 1960s, Japanese macaques moved down from the higher forests above the valley and made themselves right at home in the warm waters. These snow monkeys have been using them as a warm-up spot ever since. Spa day, anyone?