The mind is an amazing instrument.

For example, I'm terrified of roller coasters and won't get on them even when I know they've been developed and tested by stellar engineers and are maintained by famous, responsible companies like Disney.

Yet here I am in a forest in Mexico, standing 72 feet in the air on a platform less than two feet wide. I'm ready to leap off and zip along a cable high above the forest floor for hundreds of feet until I come to another tree, where I'm trusting a total stranger to keep me from crashing into it, should I fail to slow myself by gripping the cable with the right amount of tension.

But my mind, you see, has accepted the illusion that I have control, because one of my gloved hands is holding the cable, and the other hand is holding a rope attached to both the cable and a harness I'm wearing. Not only am I not terrified, but I'm rather enjoying it.

So are a lot of other people.

About a million have lined up to take an Original Canopy Tour since 1997, when Darren Hreniuk opened his first in Costa Rica. Since then, other companies have opened similar adventures, which they sometimes call sky treks or zip line tours.

Currently, there are dozens, and they've spread from Costa Rica, where they were first popularized as a tourist attraction, to Nicaragua, Mexico, Belize, Jamaica and Africa. Watch for more: It's a hot trend about to explode.

Original Canopy Tours is working on a second tour in Mexico and one in Puerto Rico. Moreover, other companies that have experience in building challenge courses are eyeing the canopy tour -- which basically takes one or more elements of a challenge or obstacle course, pumps them up, then plunks them in an exotic or otherwise tourist-friendly area. Expect to see them soon in the United States.

"We're in negotiations with seven or eight ski resorts" to bring in tourists during the off-season, says Scott Hornick, president of Grip-It Adventures. Grip-It will keep its core business of traditional challenge courses while adding zip line tours.

Hornick's firm is also working on putting zip line tours in the trees of Kauai, Fiji, Dominica and St. Lucia. He anticipates that two of them will be completed by November and open to the public by Christmas. A lot of other companies, he adds, are either considering or already moving into the field.

For now, you can zip through tropical rain forests or jungles, over an extinct volcano or within view of waterfalls. It requires only a leap of faith.

Zipping Through Mexico

After many years working in fur-trading posts in the wilds of Canada, Darren Hreniuk came back to civilization -- Vancouver, to be exact. In his words, he "joined an investor's group and became a mutual fund and insurance guy."

It wasn't a good fit. Plus, on weekend trips into the countryside, he was horrified to see 2,000-year-old-trees cut down in primary-growth forests. He started thinking.

"When I was a kid and teen, I spent all my spare time building elaborate treehouses. People loved them, and I thought maybe I could do something with them that would both help the environment and make me a living."

He started looking in British Columbia for a place where he could save the trees by renting or buying the land and setting up a canopy tour. He had in mind treehouses, zip lines, swings and bridges between trees. But when a friend told him that Costa Rica was beautiful and that rain forests were being destroyed even faster than hardwood forests, he headed that way. He spent several years experimenting, setting up the systems and finding the perfect places to put them.

The Original Canopy Tour in the cloud forests of Monteverde was an immediate hit. Although in 1998 he won a 20-year Costa Rican patent for the controlled adventure tour, others soon built canopy tours.

Last year, the government annulled the patent. It's part of a big, messy lawsuit, but in the meantime, the notion has taken off. It's so popular in Costa Rica that a study by the Costa Rican Tourist Board indicates that 25 percent of all visitors take a canopy tour during their stays.

I discover while planning for a trip to Puerto Vallarta that the activity has migrated to Mexico and sign up for an Original Canopy Tour -- one of at least three canopy tours conducted outside the resort town in western Mexico.

With about a dozen other tourists in Puerto Vallarta, I board the back of an open-air truck fitted with benches for the hour-long ride into the Sierra Madre Mountains. I'm thinking the ride is going to be my favorite part of the tour, given my fear of heights and speed.

It doesn't help that I know there are no industry-wide safety standards for canopy tours, and no oversight body.

But I'm quite comforted on arrival to find that staff members say they have been given months of training, and one staffer is assigned to every two visitors. The manager says the company has never had a serious accident -- in fact, the only accidents company-wide have been to people who stumbled on the ground on the way to the trees. The course includes 13 observation platforms, nine traverses or zip lines, two hanging bridges, a swing and, at the end, a mandatory chance to rapel back to solid ground.

We all put on helmets and step into harnesses that are pulled snug against our waists and legs. The carabiners and ropes hanging off the harnesses make me feel like a real adventurer. A series of steps up the side of a mountain leads us to a tree with two parallel cables wrapped around it.

I've since been assured by engineers that one well-maintained cable is sufficient to hold not only a person, but a house. After all, ski lifts and suspension bridges carrying trucks are held up by a single cable. But that second cable gives me the courage to jump off the side of the mountain and go sailing across the valley. A rope from my harness is attached to a pulley that's attached to both cables, so even if one cable breaks, I'm going to stay above ground and reach the platform at the next tree.

I'm wearing nifty leather rappelling gloves. Before leaping, I reach behind my head and grab one of the cables with my right hand. If I put no tension on that cable, I will zip across the forest at breakneck speed. But I can slow myself down by applying pressure -- something that's essential once I get within a couple of yards of the tree to which I'm traveling.

My guide has gone ahead and is waiting on the far platform -- both to remind me to slow down at the proper point and to physically prevent me from smashing into the tree should I fail to follow his simple instructions.

Each zip line I zoom along gets a bit more fun, because I'm less apprehensive every time. After the first couple of zips I can't wait to zip again, but that's partly because I feel so nervous about standing still on the little platforms. Explain that to a rational mind.

Safety is clearly foremost in the minds of our guides. We each have two lines with carabiners attached to our harnesses, and at least one carabiner is attached to a stationary rope or cable every second of the tour.

Of the nine zip lines on this course, the longest stretches 272 feet. The highest platform from which you jump is 72 feet above the forest floor. The swing is a Tarzan-style contraption requiring you to grab a rope and swing from the tree-top platform to the ground below. The grand finale: Your guide teaches you how to belay -- a mountaineering skill that involves holding a rope that runs through a cleat and dangles from the platform to the ground.

To make a controlled descent, you feed one of the lines through your hands until you reach the ground. To avoid sudden fatal falls by tourists inexperienced in the art of belaying, the tour operators have wisely posted a guide who stands below you holding the line so he can stop you from a free fall should you forget the instructions and just let go of your part of the rope.

The tour takes about two hours, and at the end I am euphoric. I feel that I really accomplished something, as if I had a real adventure. At the same time, like any explorer who has endured hardship with fun, I'm glad to have returned to solid ground and be done with it.

I won't likely repeat this exact canopy tour, because I've been there and done that. But throw in a volcano, a jungle with maybe some monkeys, a view of an ocean or waterfall, and I'll be up there again, zipping through life, exhilarated.

Cindy Loose will be online to discuss this story Monday at 2 p.m. during the Travel section's regular weekly chat on www.washingtonpost.com.

The canopy tour originated in Costa Rica, above, but many other countries have since added zip lines as an eco-attraction.The jungles of Belize are among the places where high-flying adventurers can take a canopy tour.Visitors queue up for the Mahogany Park canopy tour in Costa Rica.