A crown of streaming clouds flowed off the cone of Costa Rica's Arenal volcano. A sound like thunder shook the air.

Standing in a lava field about two miles from the mountainside, I watched boulders the size of Chevy Suburbans fly out of the clouds and tumble down the gray and black slope.

Oddly, the volcano's audience treated the spectacle with casual curiosity. A dozen Dutch and German tourists sat or leaned on black pumice boulders, chatting while they scoped the geological show with their binoculars.

"Doesn't this make you a little nervous?" I asked my guide, Alexander Araya.

"A little. See that lake?" He pointed to a body of water a couple of miles behind us. "The old town of Arenal is under there. It was destroyed when the volcano blew up in 1968. This thing has been active every day since. It can throw a boulder five or six kilometers."

During a four-day excursion across Costa Rica's interior, I often had the feeling that I was watching a special-effects-laden movie instead of experiencing reality. Maybe it was suddenly going from the gray world of a Minnesota winter to the saturated colors of the equatorial tropics, but everything -- the exploding volcano, the cloud forest as viewed while flying down a steel cable, a flock of iridescent hummingbirds -- seemed too extravagant to be true.

Mr. Araya, 31, added to the sense of disassociation. Perpetually clad in wrap-around shades, he told outrageous stories with disarming nonchalance and an utter lack of irony. When we checked into a hotel near the volcano, he told me not to get too close to bushes or trees with my camera because of the abundance of poisonous snakes.

"The fer-de-lance is the only aggressive one. If he sees you coming, he'll come out toward you," Mr. Araya said.

At the juncture between North and South America and between the Pacific Ocean and the Caribbean Sea, Costa Rica compresses an intense amount of geography and wildlife into a very small country (about the size of West Virginia) a few hundred miles north of the equator.

The people who live amid all these phenomena are known to other Latinos (and to themselves) as Ticos, for the Costa Rican tendency to add the Spanish diminutive to nearly every noun.

That tendency seems representative of an affectionate and nonviolent outlook on life. But while the people are nonviolent, the landscape isn't. There are more than 100 volcanoes in Costa Rica and at least five are active. Arenal, reliably rumbly, has become a hub of geo- and eco-tourism. The volcano provides heat for a number of hot-spring spas, and a dramatic setting for a number of other attractions.

Down one trail on our hike in Arenal National Park, Mr. Araya pointed out a termite mound, as big as a cluster of bowling balls, growing around a tree stump. The tiny bugs crawled around the nest.

"These are the kind that are good to eat," he said with a nostalgic sigh. "I used to eat a lot of them when I was a kid -- like candy. Now, I just can't do it. They work so hard to build that nest. I feel guilty to break it up."

That Mr. Araya would feel guilty about breaking up termite nests to eat the bugs seemed to fit the stereotype of the nonviolent Costa Rican. I had a harder time putting the zip-line phenomenon into any kind of context.

A day after leaving the volcano, I joined several other tourists in climbing a tall scaffolding, attaching myself to a pulley on a high-tension steel cable and then taking off on a high-speed journey through the upper canopy of the cloud forest.

Light rain added luster to every leaf in the jungle on the morning I showed up at Selvatura Canopy Tours in the mountain town of Monteverde. We went through a 10-minute orientation and were taught how to brake with our heavy leather gloves and how to keep our feet forward in case the braking doesn't work.

The "tour" consisted of sliding down nine cables strung down the side of a cloud forest mountain. The longest was 2,000 feet.

The zip line was fun, I admit, but it rendered the jungle a green blur. I was happy to have my feet back on the ground the next day, when Mr. Araya and I spent several hours hiking in Monteverde's main attraction: the Monteverde Cloud Forest Reserve.

At 4,000 to 5,000 feet high and straddling the country's continental divide, the reserve shelters more than 3,000 kinds of plants, 500 bird species and 120 mammals. For birders, the ultimate aim is to spot the rare resplendent quetzal, a bird with a 3-foot train of luminous feathers that might make a peacock jealous.

We hiked for miles. At times, the trail disappeared in thick fog. The moss-covered trees dripped. When the clouds parted momentarily, I could see we were walking along a ridge, with deep valleys on either side of the path.

Periodically, Mr. Araya blew a short double whistle, hoping to hear the wikka-wikka call of the quetzal in response. "When people see it, they cry," he said. "I've cried when I've seen one. There is something about them, a special energy. When one flies by, it's like the colors stay in the air behind it. I can see why the Maya thought it was a god."

Finally, a bird returned Mr. Araya's call. He set up his spotting scope and in short order identified a female, not quite as resplendent as her male counterpart, sitting in a tree about 150 feet away.

Through the scope, I saw a bird about the size of a crow, but radiating colors -- iridescent green and gold across the back, a glimmer of red near the tail and checkered black and white tail feathers. It was like a fragment of rainbow, living and breathing. A minute later, the quetzal vanished into the clouds.

"You know, once I did the zip line a few times, I don't need to do it again," Mr. Araya said. "But I never get tired of this."