Make sure to look on all sides of you while walking through the passageway. There are interesting things to see on the ground, walls and the ceiling. The Ape Caves are formed from flowing lava from Mt St Helens. The passageway progressively narrows until it comes to an end. It's amazing how large the passage is at some points. The ceiling can be 30 feet high! I recommend combining this hike with Lava Canyon, as they are both short.
I haven't done the upper route because, quite frankly, it doesn't seem worth it. I spoke with a couple whom were emerging from it and they immediately asked what time it was (it had felt like they had been in the cave for endless hours-- the darkness will do that to you). It also requires of you climbing over and through narrow portions.
Lower Passage-
- Distance: 2 miles RT
- Elevation: Negligible
- Distance: 3 miles RT
- Elevation: 500 feet
NWFP required at trailhead