Ape Caves! You'll definitely see some bats! Located at the southwest end of Mount Saint Helens, Ape Caves is a great hike. There are many ways to explore the lava tube (the longest in the continental United States): You can descend in the middle and take a nice walk in the southern tube. You can also head up the north tube, but that hike is much harder (lots of ducking and sliding through tight spaces and there is a huge ledge you have to pull yourself up onto). You can also hike up to the top of the north tube and then descend. Bring a jacket and powerful flashlight or lantern.