The steep rock face is slippery and our eyes sting from the sweat dripping down our foreheads, but our guide cajoles us as he points upward toward what he calls utopia.
A towering waterfall appears like a mirage. The tropical heat is exhausting but we get a second wind and start climbing faster toward the pool of cool water that awaits us as we hike on the "other side" of Puerto Rico's National Rain Forest - commonly called El Yunque. According to Taino Indian legend, the spirit Yuquiyu reigns from his mighty mountaintop throne, protecting Puerto Rico and its people.
Most visitors hike the well-marked paths in the northern half of the park's rain forest after being brought in on tourist buses. The trails in the south, however, have been neglected since landslides in the 1970s washed out a road from the north.
But the good news is that hikers and nature lovers can still explore far off the beaten track in the only tropical forest in the U.S. national forest system. Spanish colonizers originally set the land aside in 1876, making it one of the oldest nature reserves in the Western Hemisphere.
The town of Naguabo, a 90-minute drive from the capital, San Juan, is one of the wettest places on the island, receiving some 200 inches (508 centimeters) of rain a year. Its residents are called "enchumbaos," or the soaked ones.
Parts of the sprawling town of 25,000 border the southern edge of the rain forest. The Cubuy section of Naguabo is where botanist and organic farmer Robin Phillips lives and his guided hiking tours begin.
Phillips, who charges $75 for each group of five hikers, greets us with an orange fruit from Central America called a canistel, which has the consistency of cheesecake and almost tastes like it as well.
It's among the rare and exotic fruits from around the world that the 57-year-old native of Springfield, Massachusetts, grows on his 12 acres (5 hectares) of land, which includes a cabin and campsite for guests.
Wearing a straw hat, he points to a container filled with bamboo walking sticks and tells us to take our pick.
"Did you all pack lunches?" he asks. "It's a 12-mile (20-kilometer) hike round-trip."
We load into the back of his white pickup truck and bump along, chased by dogs, until reaching a gate blocking the rest of Route 191. About 2 miles (3 kilometers) up, landslides make the road impassable.
Signs by a riverside warn about the dangers of hydroelectric dams along the trail. In the 1990s, a U.S. Navy sailor from now-closed Roosevelt Roads Naval Station fell off a dam and was swept away by raging waters, Phillips said.
"Very few people come to this side of the rain forest," Philipps said. "And the ones that do make it alone, most are deterred by these signs."
We walk on the road for a while before veering right onto a path where the forest's lush but porous canopy allows rays of light to stream through. Phillips explains that hurricanes in recent years stripped much of El Yunque's veil-like covering.
The forest suddenly becomes hushed except for the two-tone chirp of tiny tree frogs called coqui and the twitter of birdsong, though there's no sighting of the endangered Puerto Rican parrots that live in El Yunque.
A panoply of giant ferns, banana trees and royal palms fan out overhead, among some 240 native tree species fed by the 100 billion gallons (378 billion liters) of rainwater that falls here each year.
Phillips points to a nearby stream of crystal-clear water and cups his hands for a drink, then invites guests to fill their water bottles.
"This is some of the best water in the world," says Phillips, who's lived in Puerto Rico for 20 years. "People from nearby Humacao and Fajardo fill up 55-gallon (208-liter) drums at a source near the edge of town."
Snails, large and small, crawl on the forest floor. A few minor landslides block part of the trail, forcing us to climb over.
Though not marked, the trail is easy to follow beside an aqueduct pipe covered with moss and, later, abandoned rail tracks.
Phillips picks a green fruit which he identifies as parcha, or passion fruit. He slices it open with a Swiss army knife and lets us taste the sour tang of its flesh.
Crossing another stream, he points to a felled hardwood ausubo trunk embedded into the rock. Ausubo has traditionally been used for the wooden ceiling beams of colonial houses in Old San Juan. Over the centuries, loggers have chopped down many colossal hardwoods, leaving the forest vulnerable to hurricanes.
We eventually reach a 90-foot (27-meter) ladder with metal rungs and climb slowly to the dizzying top without backpacks. The ascent is not over. We scale a maze of rocks until we reach a 110-foot (33-meter) waterfall with several levels.
At the base of one is a large pool. We strip out of our sweat-soaked clothing and into bathing suits to step into the pristine water.
"Sometimes honeymooners come up here with me," Phillips said with a chuckle. "They ask for some privacy. I go wait down below the rocks until they're done."
The cooling effects of the water quickly wear off as we lumber down the face of the mountain under a baking sun. By the time we stagger back, fresh muscle aches and a raw sunburn appear - a small price to pay for a day on the lost side of the rain forest.
If You Go:
EL YUNQUE: Also known as the Caribbean National Forest. The northern half of the park is easily accessible from San Juan by taking PR 3 to PR 191; many hotels can arrange taxis or tour buses. Robin Phillips leads 12-mile (20-kilometer) hikes from Naguabo in the southern half of the park for $75 for each group of five; details at www.rainforestsafari.com/Phillips.htm or (787) 874-2138. The Casa Cubuy inn in Naguabo www.casacubuy.com or (787) 874-6221 - has rooms starting at $90 a night. The Casa Cubuy also serves breakfast and dinner and will prepare a bag lunch for $7.