Great adventure at Gifford Pinchot National Forest. The cave/lava tube is absolutely gorgeous to look at and it is definitely a nice hike below the surface. Make sure you bring a proper lamp, good hiking boots, a sweater or even a jacket and maybe even some long pants with you. It's fairly cold 42 degrees down there and pitch black.
This is a hidden gem. The hike is fairly easy but be prepared. It doesn't get much darker than this! Bring plenty of light and batteries. It will probably take 1 to 2 hours per tunnel. One is an easy hike (rough terrain, bring good shoes!), the other is much more challenging and will require climbing over and through obstacles. Bring a jacket as it's cold all the time, and damp and drips from the ceiling a lot! Definitely worth checking out even if you don't hike the whole thing. You will get to explore about 10 feet of cave without light so don't forget the light! We liked using headlamps.
I have been through the Ape Caves seven times and that was just lately. It is a lot of fun to take first timers so anytime I find someone who hasn't gone and is interested we go. This is a fun outing any time of year. Although, in the winter the lower gate is closed so you have to walk an extra mile up the road to get to the cave entrance. If there is snow on the ground in the parking lot, don't plan on using the trail, unless you have snow shoes you'll have to return through the cave instead of using the trail. The earlier you start, the less foot traffic there will be. Personally, I am always at the entrance by 8am. A helmet is advisable but they're not cheap so if this is the only time you would use it you can do without. A hat will help protect your head from bumps but you don't want to use a hat with a bill that would obstruct your vision which will cause you to just bump your head even more. A head lamp will leave your hands free, highly recommended. Lanterns are almost useless. A super bright light will only ruin the vision of others in your party. Normal light strength will suffice. If it's raining above ground, it'll be dripping below ground. The trail back is a beautiful hike, I prefer to go up through the cave and return on the trail as it is all down hill then.
Make sure you have food shoes, a torch and a good waterproof jacket. It is a lovely spot though, worth the drive.
These caves are cool , there's also at the very end a hole and sometimes you can climb out of it if there's a log coming out of the ceiling.