Arizona's Hidden Caves and Lava Tubes: Underground Adventures for Curious Hikers
Arizona's landscapes are full of surprises -- towering red rocks, deep canyons, sprawling pine forests, and desert stretches that seem endless. But some of the state's most fascinating natural wonders aren't above ground at all... they're hidden beneath your feet.
From ancient lava tubes formed by volcanic eruptions to cool limestone caves tucked into desert mountains, Arizona's underground world holds adventure, mystery, and a refreshing escape from the heat. Whether you're a geology-loving hiker, a curious explorer, or someone seeking something truly different, these caves and lava tubes offer unforgettable experiences.
Here's your guide to the best hidden underground spots in the state -- and how to explore them safely.
1. Lava River Cave - Flagstaff
Located in the Coconino National Forest, Lava River Cave is Arizona's most famous lava tube. Formed roughly 700,000 years ago by a volcanic eruption, this mile-long tunnel stays a chilly 35-45°F year-round -- a wonderful break from summer heat.
Once you scramble down into the entrance, the darkness swallows you quickly, revealing a long, rocky corridor carved by molten lava. You'll walk across uneven basalt, duck under low ceilings, and marvel at the tube's circular shape, unique flow patterns, and cathedral-like chambers.
Why visit: Natural air conditioning, rare geology, and a sense of true underground adventure.
What to bring:
- Two light sources per person (headlamp + backup flashlight)
- Warm layers
- Gloves (rocks are sharp)
- Sturdy shoes -- the floor is rocky and slick
2. Peppersauce Cave - Oracle
Hidden at the base of Mt. Lemmon, Peppersauce Cave is a limestone cavern filled with narrow passages, clay floors, sparkling formations, and a surprising amount of moisture. This cave is wild -- meaning it's not developed, lit, or officially maintained.
Inside, you'll find tight squeezes, crawling sections, and multiple branching chambers. It's a favorite for adventurous hikers and amateur spelunkers looking for a raw, hands-on caving experience.
Why visit: Mud, mystery, and a "true caving" feel you won't find in commercial caves.
What to bring:
- Helmet + headlamp
- Clothes you don't mind getting dirty
- Gloves and knee pads
- A buddy -- never explore this cave alone
3. Cave of the Bells - Santa Rita Mountains
One of Arizona's most protected caves, Cave of the Bells sits deep within Coronado National Forest. Access requires a key from the Forest Service, which keeps traffic low and preserves the cave's spectacular formations.
Inside, you'll see shimmering pools, crystalline formations, and eerie chambers shaped over thousands of years. It's a delicate environment, so careful exploration is essential.
Why visit: It's exclusive, pristine, and feels like stepping into another world.
What to bring:
- Reservation + access key
- Proper footwear
- Respect for fragile formations -- this cave is regulated for a reason
4. Tonto Natural Bridge Cave - Payson
Technically more of a giant natural tunnel than a cave, Tonto Natural Bridge is the tallest natural travertine bridge in the world -- and you can hike right underneath it. Water drips from above, moss grows along the rock walls, and the sheer size of the opening makes you feel tiny in comparison.
Why visit: One of the most dramatic geological features in Arizona, no specialized gear required.
Safety Tips for Exploring Arizona's Underground Wonders
Exploring caves requires a different kind of preparation than hiking:
- Never go alone -- always explore with at least one partner.
- Bring multiple light sources -- darkness underground is absolute.
- Check weather conditions -- heavy rain can flood caves or make entrances dangerous.
- Watch your footing -- many caves have slippery or jagged surfaces.
- Leave No Trace -- never touch formations; oils from skin can stop their growth permanently.
Final Thoughts
Arizona's caves and lava tubes offer a rare opportunity to explore the hidden world beneath the desert -- a place shaped by fire, water, and time. Whether you're wandering through a frozen-in-time lava tube, crawling through narrow limestone passages, or standing inside a vast underground cathedral, every cave tells a story millions of years in the making.
Pack your headlamp, grab a friend, and head underground. Arizona's best-kept secrets are waiting in the dark -- all you have to do is step inside.