With access to beaches, mountains, and even sand dunes in our state, Washingtonians are spoiled for choice when it comes to outdoor adventure. If you've somehow exhausted the bounty of trails spanning both sides of the Cascades, it may be time to train your sights on routes that lead underground. Explore caves in Washington at Gifford Pinchot National Forest, where the record-breaking Ape Caves system conceals unparalleled adventure.

Gifford Pinchot National Forest is one of the country's oldest, first established in 1897. It comprises almost 1.5 million acres of alpine land between the peaks of Mount Adams, Mount Rainier, and Mount St. Helens.

We have this volcanic activity to thank for the national forest's labyrinth of caves. It's thought that the Ape Cave system first formed almost 2,000 years ago when hot lava moving beneath a hardened lava flow left behind a maze of tunnels.Scientists call these formations lava tubes, and the one at Ape Caves is the longest in the United States.

Since it was first explored in the 1950s— by a Boy Scout troop, no less— the caves have become a popular spot for hikers and spelunkers with adventure on their minds. The most popular entrance, Ape Cave Trail No. 239, receives 170,000 people each year.

At under a mile, Ape Cave Trail No. 239 is a family and beginner-friendly option for groups in a hurry or those who aren't certain how they'll fare with subterranean conditions. It can be disorienting underground and visitors must bring their own equipment. The official recommendation is two forms of light per person, not including cell phones.

For experienced visitors, I suggest the slightly spicier one-and-a-half-mile trail that requires scaling walls and piles of rock.

But if you pick the shorter route, you'll still experience the eerie majesty of the cave, whose walls tower and curve around hikers, utterly blocking out light.

Leaving no trace is never more crucial than when hikers explore caves, which are home to scores of vulnerable species. Bats play essential roles in Washington's ecology and are at risk of devastating diseases like White Nose Syndrome, which can wipe out entire colonies. To protect those living in Ape Cave, dogs are not allowed below ground, and visitors are asked not to touch the walls or ceilings of the cave.

With the cooperation of all Ape Cave hikers, hopefully, thousands more will have the chance to visit this spectacular natural attraction.

Explore caves in Washington at Gifford Pinchot National Forest's Ape Cave System. Although, keep in mind that if you do wish to enter into the caves, access is seasonal. Bring your gear and your sense of adventure for the experience of a lifetime.