Washington is full of breathtaking natural wonders, and that includes some impressive remnants of our prehistoric past. The notorious Ape Cave is more than just a fun hike — it’s also the longest lava tube in the continental United States. If you’re looking for a great trail the whole family can experience, look no further.

The Ape Cave Trail is located in the South Cascades near Mt. St. Helens.

Jonathan Miguel / alltrails.com To reach it, take Exit 21 from I-5 and State Route 503, then go straight on Spur 50, which will become Forest Road 90. Turn left on FR 83, drive for 1.7 miles, then turn left on FR 8303. You’ll see signs for the parking lot.

The caves were formed over 2,000 years ago, when Mt. St. Helens erupted and lava poured down the southern flank of the volcano.

Jason Hatter / alltrails.com You can walk through the caves in any season, but they’re specially pleasant in the spring and summer.

The trail is about 3 miles in its entirely, the majority of which involves walking through the caves.

keung h / alltrails.com The caves themselves are just over 2 miles long.

After heading down the stairs, you’ll be able to either hike the upper section or in the lower cave.

Laz & Cassie Gutierrez / alltrails.com The upper section is a bit more challenging. The lower cave is easier and shorter at 0.8 miles.

The upper cave takes a few hours to fully explore.

Danielle Sullivan / alltrails.com It requires stepping over some sharp boulders and climbing an 8-foot wall. The lower section is a lot shorter and more spacious.

The caves are open to the public, but there are some rules.

Lisa Norwood / Flickr No pets are allowed, you’re not allowed to smoke or bring food, and you should try not to touch the walls and disrupt the cave slime, a food source in the cave’s delicate ecosystem.

Make sure you wear sturdy shoes and dress in layers.

Whateverthing / Flickr Bring extra flashlights and headlamps so you don’t lose visibility.

Have you explored the Ape Caves? They’re definitely one of Washington’s most incredible attractions.

Jonathan Miguel / alltrails.com

To reach it, take Exit 21 from I-5 and State Route 503, then go straight on Spur 50, which will become Forest Road 90. Turn left on FR 83, drive for 1.7 miles, then turn left on FR 8303. You’ll see signs for the parking lot.

Jason Hatter / alltrails.com

You can walk through the caves in any season, but they’re specially pleasant in the spring and summer.

keung h / alltrails.com

The caves themselves are just over 2 miles long.

Laz & Cassie Gutierrez / alltrails.com

The upper section is a bit more challenging. The lower cave is easier and shorter at 0.8 miles.

Danielle Sullivan / alltrails.com

It requires stepping over some sharp boulders and climbing an 8-foot wall. The lower section is a lot shorter and more spacious.

Lisa Norwood / Flickr

No pets are allowed, you’re not allowed to smoke or bring food, and you should try not to touch the walls and disrupt the cave slime, a food source in the cave’s delicate ecosystem.

Whateverthing / Flickr

Bring extra flashlights and headlamps so you don’t lose visibility.

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