Located 50mls N of Vancouver, Mt St. Helen's has so much beauty of offer all year round, all four seasons giving it different terrain to see depending on the time of year. Ape Caves, near the south side of the mountain, you can walk through the longest continuous lava tube in the continental U.S. It’s a 2-mile-long dark tunnel formed by ancient lava flows. (Bring a jacket and head light: It’s a constant 42°F inside, even in summer!)