A mile-long tunnel of black lava rock in the forest northwest of Flagstaff, formed in a few hours about 700,000 years ago. It's pitch dark and cold all year, so bring two or three lights each, sturdy shoes and a jacket.
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What to bringLava River Cave · Photo: Dave Bunnell / Wikimedia Commons, CC BY-SA 4.0 · Credits
Between 650,000 and 700,000 years ago, a volcano near today's Hart Prairie sent a river of lava through the forest. The top, sides and bottom of the flow cooled and hardened first, while the molten rock inside kept moving and drained out. What it left behind is a tube about a mile long, and it looks almost the same today as it did right after it formed.
Lumbermen found the cave around 1915. Homesteaders came back season after season to cut and store the ice that collects inside.
Shine your light on the floor and walls: the rock still shows how the lava moved. The cave is also a natural refrigerator. Dense, dark lava rock keeps the sun's heat out, and cold winter air sinks in and stays all summer.
There's no lighting in the cave and the floor is uneven lava. The Forest Service advises two or three light sources each, so one failing doesn't leave you in the dark.
The cave is about 14 miles north of Flagstaff as the forest roads go, and about 19 miles by car from downtown. In winter the forest roads close.
A small vehicle fee applies, and passes are accepted. Graffiti and litter have been a problem since the late 1960s, and a major cleanup in 1991 packed out most of the litter.
US 180 starts at the north edge of downtown, so the downtown and Milton Road hotels are the quickest start. Snowbowl and the Museum of Northern Arizona are on the same road.
Photo: ExpediaIndoor pool, downtown on footMilton Road and NAU 9.0/10 on Expedia
Parking $8 a nightPets: dogs only, up to 2, up to 50 lb eachBreakfast extra
On Milton Road, one of the quickest starts for US 180, with an indoor pool to warm up after the cold cave.
Bespoke Inn FlagstaffDowntown and Southside 9.8/10 on Expedia · 426 reviewsFree parkingPets: dogs only, up to 2Check prices
Hotel Monte VistaDowntown and Southside 8.0/10 on Expedia · 1,057 reviewsParking $50 a day in a nearby lot; limited spaces at the hotelNo petsBreakfast extraCheck prices
Residence Inn by Marriott FlagstaffDowntown and Southside 9.6/10 on Expedia · 1,002 reviewsParking $10 a dayPets: up to 2 petsCheck pricesAbout 1 mile, which makes it the longest lava tube in Arizona. Walking in and back out is about 2 miles over rough rock.
The Forest Service doesn't give a time. It's about 2 miles in and back out over broken rock in complete darkness, so expect it to take far longer than 2 miles on a trail, and bring more light than you think you'll need.
Between 650,000 and 700,000 years. It formed when lava from a volcano near today's Hart Prairie erupted, and probably took only a few hours to form.
Between 35 and 45°F all year, and ice is common inside. Bring a warm layer and gloves, even on a hot day.
The cave is open all year, but Forest Roads 245 and 171 close for the winter months, so you may have to ski in.
No. Dogs and other pets aren't allowed.
For kids who can manage a mile of rough, dark ground each way, yes. Everyone needs their own lights, sturdy shoes and a warm layer.
