Grand Canyon Caverns Inn, Arizona
Most Route 66 motels just offer a bed and a shower. Grand Canyon Caverns Inn threw in a limestone cave system, the deepest hotel room on the planet, and a Cold War fallout shelter that could feed 2,000 people for a month.
Just your typical roadside stop on Route 66, and one you should absolutely try at least once in your life.
Here’s more about the legendary Grand Canyon Caverns Inn, plus how much that cave room will set you back.
Walter Peck’s accidental discovery
Local woodcutter Walter Peck almost face-planted into history when he nearly tumbled into a mysterious hole widened by heavy rains back in 1927.
Being the curious dude he was, Peck returned with some cowboy buddies. They discovered not just an awesome underground system, a ton of glittering stones.
Convinced they contained gold, our guy Walter actually bought the whole property with visions of mining wealth. Plot twist: it was just worthless “fool’s gold.”
But Peck’s epic fail became America’s roadside win.
You’ll be sleeping in dinosaur-era caverns
These limestone walls formed 345 million years ago, more than 100 million years before dinosaurs existed.
Back then, Arizona was covered by a huge inland sea, which is why you’ll see fossils of ancient sea creatures in the walls. The limestone layer here is 487 feet thick, more than the 400-foot average across Arizona.
In the lower chambers, you can see rock from 370 million years ago with 14 different fossil zones. Scientists found traces of iridium in 2021, showing that lots of meteors hit Earth when these rocks were forming.
The limestone has a pH of 8.3, which helps keep it well-preserved.
The underground rooms are pretty cozy
The caverns feature the deepest motel room in the United States, 220 feet underground. You get complete privacy after hours since the entire cavern system becomes yours.
The suite has two double beds, a living area, and a bathroom. The room stays at 56 degrees year-round with natural air circulation.
The Cavern Suite measures 2,600 square feet (65 by 40 feet). It was converted from a fallout shelter in 1962 for $18,000. The suite fits six guests with rollaway beds.
You’ll have a private bathroom, refrigerator, microwave, Wi-Fi through a relay system installed in 2019, and an intercom to the front desk.
It might help you breathe better
All the air in these caves gets completely replaced every 72 hours through natural vents. This keeps the caves free of bacteria, which is why they became a Cold War shelter.
Tests in 2022 found oxygen levels of 21.6% compared to 20.9% at sea level. The caves have much less carbon dioxide too—just 0.03% versus 0.04% outdoors.
No wonder many visitors with breathing problems report feeling better while they’re here.
A Giant Sloth Fell In 42,000 Years Ago
Not really surprising though, is it?
While exploring the caves, you’ll see the bones of a Shasta ground sloth that fell in about 42,300 years ago.
Workers found this skeleton in 1935 while getting the caves ready for visitors. The bones are still exactly where they were found. This prehistoric sloth stood 15 feet tall on its back legs and weighed 2,000 pounds.
Carbon dating in 2018 confirmed how old it is, making it one of North America’s oldest complete sloth skeletons. Scientists found 247 individual bones, which is 82% of the whole animal.
The discovery spot in Sloth Chamber is 197 feet underground and includes fur samples and claw pieces up to 8 inches long.
It was a literal bomb shelter
Fast forward to the Cold War, and this massive cave system got a government glow-up.
The feds figured a naturally climate-controlled cavern 210 feet underground was perfect for storing emergency rations in case things got spicy with the Soviets.
They stocked enough supplies for 2,000 people to live here for several weeks if a nuclear war happened. Many original items are still here, including water containers, medical supplies, and crackers made in 1963.
They also installed a radio system with a 50-watt transmitter and four generators in 1962, which is still here as a historical display.
A Mummy Lies Preserved Inside
Deep within the caverns lies a rare and remarkable find—a mummified sabertooth cat, preserved for over 10,000 years.
Discovered in a hidden alcove 150 feet underground, the feline’s fur is intact, with tufts still visible along its back and legs. Its teeth, elongated and razor-sharp, gleam in the soft light.
Carbon dating confirms the animal perished during the Pleistocene Epoch, possibly due to a sudden cave collapse. Its fur retains a faint, musty odor, while traces of ancient blood remain beneath its claws.
Serving Route 66 Since the 1930s
This is one of the few real Route 66 motels still open today. It’s been housing highway travelers since the 1930s. During its busiest years (1956-1970), the motel was 87% full and hosted about 31,000 guests.
The current building was built in 1964 and has 48 rooms in a classic motor lodge style stretching 310 feet along Route 66.
The property became a National Historic Place on April 5, 1997.
Some of the cave walls are a little electric
During your tour, guides might turn off all the lights to show you how certain crystals glow faintly when touched. Cave explorers discovered this in the 1950s when their metal equipment sparked against some walls.
The main mineral causing this is quartz, found in amounts of 0.05% to 0.12% in rock layers formed 320 million years ago. Scientists measured electrical spikes up to 0.8 volts in 2020.
You’ll see this best in the eastern part of the caves, especially in an 83-foot passage called Franklin’s Corridor, named after Harold Franklin who first wrote about it in 1957.
During storms when air pressure changes a lot, the electrical activity jumps by 340%, sometimes making visible blue-white sparks up to 2mm long.
Some People Choose It As Final Resting Place
An area called the Grotto of Eternal Peace holds the ashes of people who wanted the caves as their final resting place.
This started in the 1970s when a frequent visitor arranged to have his ashes placed in a natural alcove he loved. .
The Grotto has 27 memorial spots as of 2025. The first ashes placed here on October 17, 1975, belonged to Stanley Mason, who mapped the caves in 1952.
Right now, 14 people are on the waiting list, with the newest reservation made in 2023.
Each spot has a 4-by-6-inch bronze plaque made by Henderson Memorial Company, costing $850. The Grotto room is 40 feet across with a 35-foot dome ceiling.
Y2K Supplies Still Sit Untouched
A hidden cave room still holds survival supplies stored during the Y2K scare in 1999. The owners set up this underground bunker for a possible meltdown.
Your guide can show you sealed boxes with freeze-dried food, medical supplies, and gold coins that were never used after Y2K turned out fine.
These supplies are in a 30-by-25-foot room 185 feet underground and 320 feet from the main path. Records list 1,742 items including 640 pounds of freeze-dried food with expiration dates from 2015 to 2030.
There are also 137 American Gold Eagle coins from 1998, bought at $289 per ounce and now worth about $2,750 each.
Owner Richard Evans spent $127,400 on supplies between March and November 1999, including 24 hand-crank emergency radios made by Coleman.
Caves Have Snowflake Crystals Inside
Unlike normal limestone caves, you won’t find any icicle-shaped stalactites or stalagmites here. It’s too dry for those to form.
Instead, you’ll see rare aragonite crystals shaped like snowflakes and flowers that only form under specific temperature and mineral conditions.
Some of these formed over 200,000 years ago. Crystal sizes range from tiny to 7-inch specimens in the Crystal Garden room 240 feet underground.
The caves have 14 different types of aragonite formations, including rare “frostwork” patterns found in only 8 other cave systems worldwide.
Visiting Grand Canyon Caverns in 2025
Address: 115 Mile Marker AZ-66, Peach Springs, AZ, located 22 miles west of Seligman on Historic Route 66.
The coveted Cavern Suite can run you around $1000 a night for two people, and extra guests cost $100 each.
If you’re unable to snag it, there’s also above-ground accomodations like the Havasupai Falls Cabin and the Grand Canyon Cabin.
Tours of the Grand Canyon Caverns are available, too.
As of writing, the inn and bunkhouses are undergoing major renovations.
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