Ape Cave

Ape Cave is a lava tube in the Gifford Pinchot National Forest on the south side of Mount St. Helens, Washington, near Cougar. Depending on the source, the tunnel is two to 2.5 miles (about 3.2 to 4 km) long and formed roughly 2,000 years ago when a lava flow from the volcano followed a deep channel. In the lower section, "The Meatball", a wedged lump of lava, is wedged above the path.

There are two routes. The lower cave is about 0.75 miles (1.2 km) long, relatively easy and doable as a round trip in about an hour. The upper cave is a rough 1.5-mile route through tighter passages with a rock wall to climb; allow at least two hours. It ends at a metal ladder, and you then return above ground. The cave stays at about 42 degrees Fahrenheit (5.5 C) year-round. The Forest Service calls for two light sources per person, and lanterns can be rented in summer.

Time-sensitive (as of October 2026): the cave is open only from May 18 to October 31, with timed reservations through recreation.gov, and closed in winter (reopening May 2027). Parking requires a fee or pass. Dogs and alcohol are prohibited. Clean your shoes at the brush station so you do not spread white-nose syndrome among bats, and do not touch the cave slime.