Author: By Susan Sabin, Globe Correspondent

Date: SUNDAY, February 21, 1999

Page: M7

Section: Travel

One of our guides describes an optional hike up a nearby mountain, Cerra Chato. ``Long and hard,'' he warns, and the only views are from the top, if it's not cloudy. In that case, Arenal, 1 1/2 miles away, may be visible.

On clear days, however, Arenal is visible from all over the valley. No need to hike to see it. But after four days of walking along jungle paths at roughly the same speed as leaf cutter ants, I am aching for exercise. In this ecologically diverse country, hiking is as much about studying flora and fauna as it is about moving your legs. With 850 species of birds, 800 kinds of butterflies, and more than 10,000 plants sharing the jungles, we have found more occasions to stop and examine than to move along.

The guide cautions that the walk took him six hours, but this only encourages me.

I may be 60, but I'm fit and headstrong. So, accompanied by two guides and one fellow hiker, my husband and I part from the four others on our Experience Plus tour and climb on a bus to the trailhead.

The bus carries us to the edge of a field occupied by a single tin-roofed house. Two little girls dangle their legs from the porch and watch us cross the clearing. We wave; they stare and follow us with dark eyes to the jungle's edge.

Eduardo, the hotel guide, leads. His back spans the path. That isn't saying much. Jungle growth crowds the path from all sides; the underbrush leans toward center, branches droop overhead, and roots tunnel across it, like raised welts. Eduardo's back is soon swallowed by the encompassing green. I quicken my pace. He waits ahead, smiling. ``No need to rush,'' he says. His indulgence stings like a spur.

``I'm not,'' I lie. On prior walks, I was among the strongest. Now, being one woman with four men (make that one older woman who lobbied for a hard hike), I have something to prove. Despite the thick jungle growth, the sun penetrates. Still, it is wet underfoot, a chronic condition here in the cloud forest. I have learned the hard way that slick trails make for muddy backsides. I ask Eduardo if he can find me a walking stick. Jungle trees, protected by attacking ants, snakes, poisons, and thorns, make poor steadying posts. Eduardo claims he can take nothing off the forest floor in this, a national park, and hands me a sawed-off oar he has brought to row us around a crater lake near the top of Cerra Chato. The oar is heavy and short, but it will do.

Ten minutes later, I don't need it. The tunneling roots form a web across the path, creating bumps and depressions: ankle-breaking territory, but no longer slick. Mindful that old bones heal slowly, I keep my eyes down, using the bumps as stops, the depressions as foot holes. Farther along, the slope increases, gaining one or two feet of elevation per step. Now I plant my oar, put my weight on it, and hoist myself, one steep lift at a time. Occasionally Jose, our naturalist guide, hears an unfamiliar bird call and raises his binocs. I welcome each pause as a chance to catch my breath.

Today, with miles to make, little else warrants stopping. Howler monkeys, located by their distinctive bark, merit a brief look-see, but we pass by the wild ginger blossoms, blood of Christ bushes, or orchids that we admired on our prior four days of walking. Eventually, the slope of the path gentles and my oar becomes a burden. I change hands occasionally, hoping one of my four companions will notice and relieve me. To ask would be to declare inequality.

We walk for almost two hours when Eduardo stops to point down. There is a print of an animal on our track. ``Wow,'' says Jose. ``That's a big cat.'' Small, faint prints accompany the large one. Mother and cub. ``They are fresh,'' says Jose. We move on, each of us vying for a place behind Eduardo, who carries a machete. It's every man for himself and even my normally solicitous husband, a serious puma-phobe, manages to insert himself near the front of the pack. I am last. This is only one of my problems. My bladder is bursting. With all the men ahead, it is my one opportunity to squat, but I dare not. I've seen enough animal kingdoms to know that pumas salivate when they see a small straggler.

About a half hour later we reach the top -- a 1,500-foot elevation gain in four miles.

Two and half hours in all. Not bad. A clearing hacked out of the jungle provides a small window on Arenal. And on this, a cloudless day, we have a clear view. Jose, our walking encyclopedia, tells us that after 500 years of dormancy, Arenal first erupted on July 29, 1968. It roared on and off for 48 hours, destroying five square miles of farmland and 78 lives. It has been exploding, off and on, since. Volcanologists say that Arenal's eruptions are small enough for tourists to safely visit the surrounding national park, but warn they are erratic enough to warrant respectful distance.

From this perspective, the distance between Cerra Chato and Arenal seems insignificant. The view I didn't come for is surprisingly compelling.

In the clearing, we stake out viewing rocks and lather fresh insect repellent on pungent bodies. While I sip from my water bottle, I unwrap my leftover breakfast: a corn tortilla stuffed with a mix of scrambled eggs and ``callo pinto'' (black beans and rice). Cold eggs never tasted so good, so self-satisfied am I. We stretch our lunch break to give the volcano a chance to perform, until finally we rise and pack our leftovers.

The men are already filing out of the clearing when a silent rush of steam pushes skyward. ``Hey, hey, stop,'' I scream. Everyone turns. A second later, the mountain roars. A cloud of pulverized rocks shoots up and up, seeming to gather energy as it rises. The mountain roars again, and then again, leaving after-sounds like cymbals that continue to vibrate. The cloud spreads like the mushroom cap of a bomb, bursts sideways from center like fireworks, and cascades downward, all at once, and all while fresh ammo is rising. The energy is violent, beautiful, thrilling.

In less than three minutes the show is over. The walk down takes considerably longer. Yet despite knee-challenging drop-steps, it feels like a float. At every opportunity, we turn and reach out to assist one another; to exclaim, review, gloat at our exquisite timing. The explosion has bound us. We are a team.

Room rates: They range from $64 for double, $118 with breakfast and dinner. Some rooms have a view of Arenal.

What to do: There are entry fees to all national parks in Costa Rica, and entry fees as well to some other sites such as Tabacon Resort, a hot mineral spring spa with a restaurant, mud baths, outdoor and indoor pools, and water slides. We visited the no-frills version (Aguas Termales de la Marina) across the street, where hot spring water rushes down a series of pools set into a hillside at the edge of the jungle. Birds flitted overhead and howler monkeys swung in the trees.

Fortuna River Falls, about 3 miles from Fortuna, also has an entry fee. A one-mile hike down a mountain side leads to the base of steep waterfalls. Water pounds into a natural rock bottomed pool where visitors can swim. Arenal Botanic Gardens, about 2.5 miles east of Nuevo Arenal, display about 1,200 species of plants. (There is an entry fee; call 694-4273).

Additional information: Costa Rica Tourist Board: 800-343-6332. For walking tours of Costa Rica: www.specialtytravel.com/walkcrica.html.

We traveled with Experience Plus Bicycle & Walking Vacations of Fort Collins, Colo. Telephone, 800-685-4565.