The traveling public has had lush Costa Rica on its radar for at least a decade. But Bosque (pronounced BO-skay) keeps a low profile. At cocktail hour, strangers ask, “How did you hear about this place?” Almost universally the answer is, “word of mouth.” That’s how my husband and I found it—through a friend who lives near here half the year.

Set amid 650 acres of rain forest, the resort perches along the edge of Cape Matapalo. It’s “on the Osa,” as locals call the Osa Peninsula—suspended between the Pacific and the Golfo Dulce (“Sweet Gulf”) near Panama. Water vistas unfold from Bosque’s 10 cabinas and a house. A tropical garden embraces another house and three cottages. The rest of the acreage is for close to 800 species of mammals, birds, butterflies, amphibians, and reptiles listed in guest handbooks as “frequently seen or possible to see at Bosque and its surrounding area.”

Those staggering numbers make it hard to imagine this rich terrain once was slashed and burned for cattle-grazing. It was an abandoned pasture by the time 20-something Floridian Phil Spier began surfing off this coast in the 1980s. But Phil’s attraction to Cape Matapalo jutting into the Pacific compelled him to buy a piece of it in 1987.

“The owners were really excited that this gringo came along and wanted the ‘trashland,’” says Phil’s wife, Kim. A former San Francisco attorney, Kim has been part of Bosque for eight years. “Phil started with 250 acres,” she says. “He worked two jobs, maxed out his credit cards, borrowed money, lived here in a tent, bought more acres.” As he built cabins and planted trees, the rain forest began to rebound. “Now the whole forest has come back in just 18 years,” Kim says. She gestures to towering trees where the daring acrobatics of capuchin monkeys captivate guests. “There are pumas, wild pigs, ocelots. People who come here are really into wildlife,” she says. “They don’t just come to check ‘rain forest’ off their lists.”

At the small resort, the mostly Costa Rican staff gives lots of personal attention. Waiters Freddy and Eylin issue a warm buenos días as guests meander to breakfast for rich Costa Rican coffee and traditional foods such as beans and tortillas, with eggs. Freddy and Eylin coach a little Spanish—and Freddy welcomes additions to his English vocabulary. When I finally learn to say terminé, to indicate I’m finished with the addictive banana pancakes, Eylin’s smile metes out the equivalent of a gold star.

After breakfast, visitors can “thrill” or “chill.” For the former, choices range from zip lining in the forest to surfing some of the Pacific’s best waves. For the “chill” factor, forested switchbacks lead to natural-spa tide pools for a surf-kissed soak. Hiking can be gentle or taxing, guided or not. Bosque perches high on Cape Matapalo, so walking to the Golfo Dulce takes about an hour, to the Pacific about 15 minutes. Then there’s the climb back up.

After such treks, guests use Bosque’s blackboard to chalk up names of wildlife they spy on the trails. But guide Philip Davison says, “The only living creatures I can guarantee you’ll see in the rain forest are termites and ants.” Strange as it seems, that turns out to be pretty exciting. Our group soon appreciates termite nests, which look like old knapsacks draped onto tree trunks but that are vital to this ecosystem. Lines of leaf-cutter ants, each hauling greenery twice its size, fascinate us.

The resort can make arrangements to sample a bit of the Osa beyond Bosque. As a romantic alternative to Bosque’s delicious dinners—served family-style so guests can swap stories of the day’s adventures—nearby Lapa Rios Ecolodge makes a lovely choice. Also worthwhile is Lapa Rios’ “Medicine Walk” through the rain forest with biologist and indigenous shaman Danilo Alvarez. Participants see botanicals for everything from baby powder to surgical sutures.

For another terrific experience, Bosque can set up kayaking expeditions with outfitter Escondido Trex. While paddling, we ask guide Josh Sibley about Costa Rica’s lack of a military force. “Oh,” Josh says, “The pelicans and the frigate birds are our air force. The turtles and dolphins are our navy. We’re peaceful.”

Josh moved here from Seattle because, he says, “the Osa has everything I love. Costa Ricans know they have something special, and they want to share it. They’re happy to see tourists come.” Then he adds with a laugh, “Maybe it’s because they know you’ll be leaving.”

When that time comes for us, we’re heavy-hearted. Freddy takes our breakfast dishes away, and I tell him lo siento de salir, I’m sorry to leave. I make fists and touch my eyes to symbolize tears. Freddy balls a fist with his free hand and holds it to his eyes. “También,” he says, and I feel that he truly means it, that he also is sad to see us go.