This is a short hike/spelunking trip worth the time if you are in the area. Essentially this hike takes you through an ancient lava tube. The tube was exposed when some lava deposits on the surface collapsed and made an accessible opening.
You will need lights for this hike as there is no sunlight once you are inside. Unlike caves back east, this is a cold cave, with temperatures ranging from 32 to 40 degrees. There are many types of lava deposits inside the cave, but none of the typical formations one might expect. The ceiling is arched and rounded in most places, hence the subway tunnel description. The floor is smooth in some places, covered with rough, sharp lava deposits in some, and in some areas covered with loose rocks. There is not much elevation gain that we could tell. The biggest challange comes from loose footing.
Okay, so on to the "hike". From the parking area, it's a short jaunt to the mouth of the cave. There is a big circle of lava rocks marking the entrance. There is an interpretive sign outside that says bats, porcupines, and squirrels occasionally use the cave for shelter, but we didn't see any signs of critters other than human ones!
You start out by climbing down a rock fall into the tunnel. The ceiling quickly opens up so that you can walk upright. The ceiling is actually really pretty. When we were there, the roof and some walls were covered with water droplets that sparkled whenever a headlamp caught them. The rocks in this area tilt and slip quite a bit so watch your step.
As you progress further into the lava tube, the cave splits into two tunnels. If you stay to the right, the ceiling gets quite low in spots, so watch your head and your back. If you stay to the right, you can stand up the whole way, but what fun is that?! These two tunnels rejoin each other shortly and end in the same place.
The lava tube basically dead ends and you go out the way you came in. It's not particularly spectacular as far as caves go, but pretty amazing geology wise. There are areas where large slabs of rock fell from the ceiling and you can almost imagine the lava splashing away from it from the dried patterns on the floor.
We had the most fun just turning off our headlamps and experiencing the darkness and absence of sound. It's also fun to play mind games with your hiking parnters. It's amazing what your imagination can dream up with a little encouragment! We started around 11 AM and had the place to ourselves. We did this with head lamps which makes for an easier walk with your hands free. We did see a few folks with flash lights. Whatever you do, I'd recommend at least one form of light per person and back up batteries! Gloves would be a nice luxury, but are not necessary!