How to See the Ape Cave
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One of Washington’s most adventurous hiking trails is through the Ape Cave, a 2.5-mile lava tube buried deep under the Gifford Pinchot National Forest. Eruptions from Mount St Helens formed the cave 2,000 years ago when the surface of a lava flow hardened and its center flowed out, leaving behind an enormous underground passage. Two trails explore the Ape Cave. One is laidback and family-friendly. The other is a challenging journey with at least as much climbing as hiking. Whichever you choose, here is everything you need to know about visiting Washington’s Ape Cave.
The Ape Cave is a 2,000-year-old lava tube
Know before you go
The Ape Cave is open seasonally from mid-May through the end of October.
You need a 2-hour timed reservation to visit the Ape Cave, plus either the NW Forest Pass ($5/day) or America the Beautiful Pass. Details below.
Dogs are not allowed in the Ape Cave.
The Ape Cave stays about 42 F (6 C) year-round. Bring warm clothes. You’ll feel silly in the parking lot on a hot summer day, but trust me, you won’t once you’re in the cave.
Stop at the vault toilets on the way to the cave entrance. It’ll be a while before you have another opportunity.
You need at least one light source stronger than a cell phone light to enter the cave. You can rent flashlights on-site ($5). It’s better to have two light sources per person, both to provide enough light and in case one malfunctions.
Try to avoid touching the cave walls or ceiling, which disturbs the cave ecosystem.
Passes and reservations
You need two passes to visit the Ape Cave:
NW Forest Pass ($5/day) or America the Beautiful Pass. You can buy a pass ahead of time or on-site.
Timed reservation ($2). Make a reservation at recreation.gov before heading out. From what I saw, they aren’t hard to get if you book slightly in advance. I looked on Thursday night and got a reservation for Saturday. By Saturday, they had sold out. The Forest Service website says that you need to print a physical copy of your reservation confirmation, but go ahead and ignore that. Digital copies are fine. A ranger will check your reservation when you arrive. The reservations are for 2-hour visiting windows. Arrive at the beginning of the window.
White Nose Syndrome
Use the boot brushes before and after seeing the Ape Cave
White Nose Syndrome is a fungal infection that is harmless to humans but deadly to bats. Human visitors can unwittingly spread the fungus when they visit multiple caves by carrying it on their clothing. Bats don’t hibernate in the Ape Cave but they do visit sometimes. You almost certainly won’t see a bat while you’re there. Tell a ranger if you do, they keep track.
Here is what you can do to avoid spreading White Nose Syndrome:
Have a dedicated set of clothes and shoes for the visit. Don’t wear anything that has been in another cave. The fungus can linger even after washing. Likewise, don’t wear the clothes you wore in the Ape Cave to another cave in the future. I suggest taking a picture of your outfit so you remember.
Use the boot brush before you enter the Ape Cave and after you leave.
Leave your dogs at home. They can be carriers of the fungus.
Don’t bring food into the cave.
Disinfect gear (camera, water bottle, etc) with alcohol wipes if they won’t damage the gear.
If you see a bat, don’t touch or disturb it.
What to bring
Two light sources per person. Cell phone lights aren’t strong enough. A headlamp is a good choice since it keeps your hands free. For the other, I’d suggest something like this camping lantern that you can carry hand-free or point like a flashlight.
Extra batteries. I learned this one the hard way.
Warm jacket, hat, and gloves.
Sturdy shoes. Waterproof hiking boots are ideal.
Water bottle. Cave exploration is thirsty work and drinking water isn’t available on-site.
Small day pack to stow your water, phone, keys, and such.
Bring two light sources per person to the Ape Cave
What not to bring
Food is not allowed in the Ape Cave. I’d leave some snacks in the car for after the hike.
Don’t wear clothes you’ve worn in another cave.
Don’t use a child carrier backpack in case of low places in the ceiling.
The Ape Cave Trails
A staircase descends from the surface into the Ape Cave
Two trails begin at the Ape Cave entrance. If you do both, it’s a little under 5 miles of hiking.
The 1.5-mile out-and-back Lower Cave Trail is easy and family-friendly.
The 1.5-mile Upper Cave Trail is a difficult journey that involves climbing over rock piles. You’ll exit the cave at the end of the trail, and then hike another 1.5 miles through the woods to return to the entrance. I’d skip this one with kids younger than eight.
A sign points the way to the trails
Other than the difference in terrain, the two trails are pretty similar. I did both since I knew I’d be writing about them, but don’t feel like you’ve missed anything major if you do one or the other. It’s mostly about how hard you want your day to be and how much you enjoy climbing on things.
If you dislike small spaces, I’d suggest the Lower Cave Trail. The ceilings are high and the walls spread pretty wide. If you’re fine in an elevator, you’ll be fine here. The Upper Cave Trail has narrower passages but nothing extreme. If you find yourself in a place where you need to crawl, turn around. You’ve either reached the end of the Lower Cave Trail or you’re going the wrong way.
The Ape Cave entrance is a place where the lava tube’s ceiling collapsed
Lower Cave Trail
Distance: 1.5 miles out and back
Elevation gain: 200 feet
Difficulty: Easy
Kid-friendly: Yes
Time: 1-2 hours
My friend Adrian leads the way down into the Ape Cave
The Lower Cave Trail is the easiest way to explore the Ape Cave. From the parking lot, you’ll walk about a quarter mile to reach the gaping hole in the earth that is the cave’s entrance. As you take the stone stairs down, you’ll feel a growing chill from the cave air. Once you reach the bottom of a second, metal staircase, you’ll be inside a 2,000-year-old lava tube. A sign points toward the Lower Cave Trail.
The Lower Cave Trail
From here, the journey is straightforward. You’ll want to watch your footing in the darkness, but you won’t run into any major obstacles. The Lower Cave Trail feels surprisingly spacious. You’ll be able to pass other hikers with room to spare. At times, the ceilings are high enough to feel like an underground cathedral. Tiny stalactites called lavacicles hang from them.
By studying the walls, you can get a sense of the Ape Cave’s geology. Ridges act like high water marks, suggesting the level of different lava flows that passed through over several hundred years. Glossy surfaces show where hardened rock remelted as lava flowed past it. The rock here is basalt, a rarity in the Cascade Mountains. Unlike more silica-rich lavas, basalt is runny enough to form lava tubes.
The highlight of the Lower Cave Trail is a rock formation called The Meatball. This eye-catching sphere sits lodged between a narrow spot in the cave walls. A lava river would have carried The Meatball to its current position.
The Meatball
The Lower Cave Trail is over when you reach a dead end. The ceiling gets lower until it barely accommodates a crawling adult. If you’re determined, it’s possible to crawl under but you’ll still reach a dead end, plus be all wet from wriggling on the cave floor. From here, return the way you came to exit the cave or take the Upper Cave Trail.
The Lower Cave Trail ends at a dead end
Upper Cave Trail
Distance: 3-mile loop (1.5 miles in the cave, 1.5 miles on the surface)
Elevation gain: 400 feet
Difficulty: Hard
Kid-friendly: For older kids (8+)
Time: 2-3 hours
The Upper Cave Trail starts at the same place as the Lower Cave Trail, the base of the cave entrance stairs. For a moment, it will seem as flat and easy as the Lower Cave Trail until you encounter the first of many rock piles. I’ve seen other sources say that the Upper Cave Trail has 27 of them. I’ll admit I didn’t count but can confirm there are a lot. The piles come from areas of ceiling collapse in the cave, a fun fact I tried to forget as I clambered over them. The journey isn’t technical, just slow and tiring. The darkness and some unstable rocks make it more difficult to keep your footing. You’ll want to have both hands free.
I study the “trail”
The Upper Cave Trail continues for 1.5 miles before ending at a staircase that will bring you back to the surface. The terrain alternates between flat stretches similar to the Lower Cave Trail and piles of chunky boulders. Take your time and wear clothes that can get dirty.
Some boulders to squeeze past on the Upper Cave Trail
With one exception, I found the Upper Cave Trail easy to follow. Toward the beginning of the hike, a large rock pile fills a wide part of the cave. I went straight over it and found a dead end. After climbing back up, I saw the trail continue to the right instead. From here, it was just a matter of getting over and around the obstacles.
Some debris to climb over on the Upper Cave Trail
The most physically challenging (and most fun) part of the Upper Cave Trail is an 8-foot wall that you climb. You’ll reach it about halfway through the hike. There’s a rope to help you pull yourself up while bracing with your feet.
A rope aids the climb up an 8-foot rock wall
The first half of the Upper Cave Trail was strangely deserted when I visited. After leaving behind the weekend crowds on the Lower Cave Trail, my caving buddy and I had the Upper Trail to ourselves for about a mile. Then, we ran into a bottleneck. I learned later we had caught up with a 72-member church youth group.
It was slow going from here. Much harder than any other aspect of the hike was hearing six dozen animated voices reverberating off the walls of a confined space for over an hour. Not to mention the pushing. I’m guessing that getting stuck behind such a large group is unusual, but be prepared to spend longer than you intended in the Ape Cave in case of the unexpected.
On the second half of the trail, a few mossy skylights add beauty to the journey. Again, try not to dwell on the fact that ceiling collapse formed them.
A skylight lets in sunlight into the Ape Cave
The Upper Cave Trail ends at a ladder that will bring you back up the surface. You’ll feel a rush of warmth about halfway up. Even on an overcast day, the daylight will seem unusually bright.
Exiting the Ape Cave
After leaving the Ape Cave, take the dirt path through the woods back to the parking lot. It is gentle and flat enough to make it feel effortless after navigating so many rock piles.
Take this trail to return to the parking lot
Although near Mount St Helens, the south side of the mountain experienced less impact from its 1980 eruption and mature trees surround the trail for most of the hike.
Follow this trail to return to the parking lot
Tall white stalks of beargrass start blooming along the trail in June. Look for penstemon, violets, and some lingering bleeding hearts in the undergrowth.
Beargrass
After an easy, 1.5-mile walk, you’ll be back at the Ape Cave entrance. Stop by the boot brushes again before heading out.
Trail of Two Forests
Distance: 0.25-mile loop
Elevation gain: Minimal
Difficulty: Easy
Kid-friendly: Yes
Dog-friendly: Yes. Unlike the Ape Cave, leashed dogs can visit the Trail of Two Forests.
ADA access: The boardwalk trail is flat and even without barriers like steps.
Amenities: Restrooms and picnic tables
Beargrass blooms along the Trail of Two Forests
After you visit the Ape Cave, I highly recommend stopping at the Trail of Two Forests a half mile down the road. This short interpretive trail explores an eerie landscape that tells the story of volcanic destruction. Around 2,000 years ago, Mount St Helens erupted, covering what is now the Trail of Two Forests in lava. This lava cooled around tree trunks and fallen logs. The trees burned away, leaving behind hollow casts.
This hole records the diameter of the tree that once stood here
The forest has since regrown, and mature trees shade the boardwalk trail. The highlight of the trail is The Crawl. A ladder leads down into a tree cast, connecting with a tunnel that reemerges about 30 feet away. Both times I visited, the trail was mostly deserted except for kids going through The Crawl over and over again while their parents said, “Really, again?!” If you’re visiting with kids, consider bringing reading material. You might be here a while.
This ladder descends into a tree cast that connects to a tunnel
Getting there
To reach the Ape Cave from Portland, take I-N until Exit 21 toward Cougar/Woodland. Turn right onto WA-503 S and continue for 35 miles. Turn left onto NF-83 and follow it for 1.7 miles. Then, make another left onto NF-8303. Drive a mile and you’ll reach the kiosk where you’ll check in with the ranger. The roads to the Ape Cave Interpretive Site are paved and no problem with a low-clearance vehicle. The drive from Portland takes about 90 minutes.
After you park, follow the dirt trail about 0.1 miles to reach the information booth, restrooms, and gift shop. You can rent lights here if you need them. Use the boot brushes, then take the trail next to the gift shop for another 0.1 miles to reach the staircase to the Ape Cave.
Explore nearby
Find incredible views of Mount St Helens on the trail to Goat Marsh Lake.
For a cave adventure in Oregon, check out the Lava River Cave near Bend.
