Entry No. 57 — the Seattle file — filed under: roadside-oddity

Ape Cave Lava Tube

Formed about 2,000 years ago by lava streaming down Mount St. Helens, Ape Cave is the longest continuous lava tube in the continental U.S. at roughly 2.5 miles. There are no lights inside, so you descend the staircases into total darkness with your own headlamp; the easier Lower Cave is a one-hour family route, while the Upper Cave demands rock scrambles and scaling an 8-foot lava wall. It's a genuinely otherworldly, pitch-black underground walk through a volcano's plumbing.

The move: Bring headlamps and a thermos, descend into the pitch-dark lava tube, and feel the temperature drop as you explore the Lower Cave together.

📍 Before you go Timed entry reservation (about $2) plus a Northwest Forest Pass required; bring your own light and a warm layer (cave stays ~42F). Seasonal, generally open late spring through fall.

• 📍 Cougar / Mount St. Helens, WA
• 💸 Free
• ⚡ Up for anything
• 🌗 Outdoors

Where: Ape Cave Interpretive Site, Gifford Pinchot National Forest, Cougar, WA

Hours: Added 2026-06-24 — confirm current hours before you go.

⚠ Seasonal or scheduled — always check before you go.

Plan a visit & invite your people →

Proof: source 1 · source 2 · source 3 · source 4

last checked: 2026-06-24