Peering down from atop Cerro Negro volcano, it's easy to see how a daredevil on a bicycle earned a land speed record gliding down its cinder cone slope.
The drop is a stomach-churning 41deg angle, for nearly 600m.
Tourists do it for fun.
The instructor laid out the drill. He would give each of our simple sleds a push, and we would hurtle down the slope as fast as we could, a weird bobsled run through hell.
"Most of the people, when they get down to the bottom of the volcano, are always wishing they went faster," Anthony Alcalde said by way of encouragement.
Not me. I was just hoping to survive.
Volcano-boarding is the latest and most unusual adventure sport to hit Central America, and it's only done on Cerro Negro, a 730m-high active volcano that's one of a string of some 25 volcanoes that traverse Nicaragua.
Some of Nicaragua's jungle-covered volcanoes are majestic and verdant. A few send off plumes of gases. Cerro Negro, which means "black hill", is neither handsome nor imposing. Rather, it is a belching mound of black cinder with a cone indented by two craters.
It is Central America's youngest volcano, spewing to life in April 1850 and erupting more than a dozen times since, most recently in 1995. It remains distinctly active. Dig into the cinders a bit with a shoe, and one feels heat.
At least three tour companies operate volcano-boarding trips to Cerro Negro from Leon, the one-time colonial capital of Nicaragua and the closest city.
The first person to come up with the idea of sledding down the volcano's cinder slope was an Australian.
"He decided to go down the volcano on surfboards, French doors, mattresses, anything he could find. Then he came up with the idea of the board we have now, the wooden board with the Formica [bottom]," said Gemma Cope, co-owner of Bigfoot Nicaragua, one of the tour companies.
A French cyclist, Eric Barone, brought Cerro Negro to the attention of adventure seekers.
In 2002, Barone sought the bicycling land speed record pedalling down the slope of Cerro Negro. He already held mountain-bike speed records, mostly on snowy slopes in the Alps.
In a first attempt, Barone went down on a serial production mountain bike, hitting 163kmh.
Then he re-ascended and mounted a custom prototype bicycle, zooming downward even faster. Barone hit 172kmh before calamity hit. His front tire blew and his frame collapsed, all recorded on video.
"I do recommend you take a look at this on YouTube," Alcalde tells us after we've huffed our way along a rocky path up Cerro Negro, carrying our individual sleds, and are preparing to descend. With the blowout, Barone "landed 100 yards [90m] past the bike. He was hospitalised for three months here in Leon with broken ribs, bones, ligaments," Alcalde says.
Worse, while he was recovering, an Austrian came to Cerro Negro and broke the mountain-bike speed record Barone had just set, reaching more than 164kmh. Barone still holds the prototype bike speed record.
Each of us has been given a canvas bag containing a bright orange jumpsuit and green goggles. Alcalde showed us how to sit on the wooden sled, which is nothing but a piece of plywood with a crude seat and a rope handle. Formica had been placed on the bottom to reduce drag. The only brakes are heels plunged into the cinders.
At the bottom of the slope, a tour company employee aimed a radar gun, clocking the speed of each sledder.
The top speed among the 17,000 people Bigfoot Nicaragua has sent down the slopes is 87kmh, held by a woman.
One by one, the Australians, a Scotsman and two young American women in our group push off, kicking up a cloud of dust as they gather velocity. A few tumble off their sleds partway down.
A lump gathers in my throat, made worse by a comment from a friend who wonders if I might win the "most stupid dad" award for letting my daughter plunge down the mountain. I was glad her mother decided to take a pass on the adventure.
It was her turn, then mine.
The sled starts out slowly but quickly gathers speed, swooshing over the tiny rocky cinders. Cinders pile around my legs as dust and sand pummel my face. I remember to keep my mouth shut.
When I get off the sled at the bottom, I take off the goggles and see a jubilant Sara Marie Sanders. Soot smears her face, setting off her huge white smile.
"Oh my gosh, it was absolutely amazing. You can't really tell how it's going to feel until you're going down it," Sanders said. "I would do it over again 100 times."
Organisers say the only common injury is a light gravel rash. Volcanic pebbles can be sharp. It's ill-advised to put hands down unless one is wearing gloves.
After a bumpy 45-minute ride back to Leon, the Australians gather in a pool at the hostel where Bigfoot Nicaragua operates, reliving the thrill.
"It's one of the best things I've ever done, hands down," said 24-year-old Michael John David. "I've snowboarded, surfed my whole life. And it was an epic day today, loads of fun," echoed Poochie Davidson, another Australian.
"It's the novelty factor. Like, how many people can say they bombed down a volcano in their lives and had a cold beer at the bottom?"
Volcano-boarding adds to other activities - including surfing and jungle zip-lining - that place Nicaragua on the adventure trail. Long overshadowed by Costa Rica to the south, with its developed tourist industry, Nicaragua has its own lustre.
"People who come up here from Costa Rica always say, 'I love Nicaragua. Everything is cheaper'. But it's not just the economics," Alcalde said.
Cope of Bigfoot Nicaragua chimes in: "It has amazing jungles, it has great mountains, it has beautiful beaches, it has colonial cities, and the culture of the people, you know, is incredible."
Last but not least, there's a lot to "lava" about speeding down a volcano.
If you go
• From the Nicaraguan capital, Managua, you can rent a car or take a bus on the 75km trip to Leon.
• Where to stay: Many travellers stay at the Bigfoot Hostel (www.bigfootnicaragua.com) where rooms can be had for $US7 a night, or many other hostels in Leon. For travellers wanting a more elegant experience, try the El Convento boutique hotel on the site of what was a 17th-century convent. Rates vary from $US85 to $US113 a night ($NZ113-$150).
• www.elconventonicaragua.com. How to arrange a volcano-boarding excursion: Bigfoot Nicaragua offers the five-hour tour for $US23 ($NZ30).
• Tierra Tours (www.tierratour.com) also offers a five-hour trip that costs $US35 ($NZ40) each for one or two people, $US30 each if the group is larger. In most cases, you will also need to pay a $US5 ($NZ7) entry fee into the Pilas El Hoyo natural reserve.
