Mount St. Helens is a somewhat dormant volcano. It last erupted in 2008; more memorable was the deadly eruption in May, 1980.A discovery of lava tubes near Mount St. Helens was made in 1947. The Ape Cave dates back almost 2,000 years. A youth group named the St. Helens Apes were the first to explore and navigate the caves (the caves/tubes were named for them). Today, these pitch black caves can be experienced by anyone with a bright light. There are two caves to explore. The lower cave is shorter and easier (that we did). It has a few interesting features including what they call a meatball and train tracks. Unfortunately, my flash and my flashlight were unable to capture a photo of them. The tunnel descends for three quarters of a mile and gets narrow in areas. It is sort of onion shaped with textured volcanic walls, rocky ground and pointy Cathedral ceiling. The upper cave, which we opted not to navigate, is longer and has more than 25 breakdown boulder areas to cross over in the dark. (I need both hands free and lots of light to scramble over volcanic rocks). There are other hikes in the area above ground. We did walk above ground through the lush forest for a while.The Ape Cave is part of the National Park system. There are plenty of rangers available to answer questions and rent you a lantern. Although it was cool above ground when we visited, a consistent 42 degree tunnel can keep you cool on the warmest of days. It is an interesting place to visit and lots of families do visit. The intense darkness lets your eyes and mind discover new patterns and exciting possibilities. The only Ape noises you will hear are coming from children and some adult humans.