Ape Caves

Ape Cave formed about 2,000 years ago, when lava from Mount St. Helens drained out of a tube and left a tunnel more than two miles long. A logger found it in 1947, and it's named for the "St. Helens Apes," a local outdoors group who explored it in the 1950s.

The lower cave is the easy one: about three-quarters of a mile each way on a mostly flat, sandy floor, and it's where you'll find the Meatball. The upper cave is about a mile and a half of scrambling over rock piles, including an eight-foot lava ledge, and you hike back above ground.

It stays around 42°F inside all year, so bring a jacket even in August. Timed-entry reservations are needed in the busy season, and pets aren't allowed in the cave.