Looking behind me as I clambered out of the river, I saw what Pedro was concerned about: a huge brown wall of water, high, wide and powerful, roared over the waterfall, one of five that tumble down one after the other on the Yaguey River in this unknown and seldom-visited area 20 kilometers up in the mountains off the southwestern coast of Cuba.

We had taken a four-wheel drive road from the Marca del Portilla hotel on the Caribbean coast, first stopping for coffee and sweets at the clean, neat farmhouse where Pedro and his family live. The bumpy dirt road is used mostly by goats, cows, pigs and horses, and we had to make sure to close the gates behind us as we drove up to keep the animals from following us. Then we rode horseback down to the falls.

It had rained early in the day and now, hours later, the water had gathered from the high mountain valleys and gullies to suddenly burst over the cliffs in a raging torrent. "Today was your lucky day," Pedro said as we watched the water rise higher and higher. "You had an exclusive; you are the first tourists to see that, because people are not taken to the falls when it rains."

Then he added, "Este rio es el corazon de Sierra."

And the heart of the Sierra Maestra beats green, fecund and fresh, I discovered during a week's visit in October to attend the third annual TurnNat eco-tourism conference. Untouched by development and protected from encroachment by its isolation and the U.S. embargo, the southern coast of Cuba features an incredible range of plants and animals, everything from Cuban pygmy owls and Zunzuncito bee hummingbirds (the smallest in the world), to frogs the size of your thumbnail, rare lizards, butterflies with invisible wings and scores of endemic species found nowhere in the world but Cuba.

It is one of the ironies of the embargo that what contributes to the isolation of the Cuban people also has isolated its mountains and national parks, allowing wildlife to thrive. Nature flourishes here to such a degree that National Geographic recently wrote that the biodiversity of Granma Province, where the Yaguey Falls are located, and the rest of this part of Cuba, is as great as the Gallapagos Islands. And that is what makes it such a pleasure to visit the vast area, free from the development that is sweeping through so much of the world's pristine areas.

This is the "other side" of Cuba, far from the nightlife of Havana, with primary forests and near-pristine areas that are off the normal tourist track. Now, the Cuban government's Flora and Fauna enterprise, hoping to draw nature lovers and their dollars to the beleaguered island nation through an emphasis on eco-tourism, is highlighting the national parks, green mountains, fast-moving rivers, and endemic birds and animals of the region.

"Cuba is a paradise for eco-tourism. The potential and beauty here is incredible," says Boulder's Robert Walz, president of Cancun, Mexico-based Last Frontier Expeditions and Safaris, an international travel provider who has registered the domain name www.cubaecotours.com and who is one of the pioneers in leading eco-tours to Cuba.

Added Walz, who also offers eco-tours to South Africa, Honduras and Nicaragua, "I've been all over the world, most of the countries of Africa and Asia and South America, and Cuba's eco-tour potential is as good as all of them. Once tourism opens up, Americans are going to be amazed at the amount of pure nature in Cuba."

I saw quite a bit of that nature during my short stay.Whether many of those tourists will be Americans remains to be seen. The Bush administration recently announced a tightening of the 40-year old travel ban, but the Senate and the House both voted recently to lift the ban. And the U.N. General Assembly voted once again, by a vote of 179-3, to end the embargo.

The people in charge of the Cuban eco-tourism industry would fit in well in Boulder. I found the officials, such as Loreta Garcia Sardina, subdirector of Flora and Fauna, genuine, funny, and exuding a real love of nature. What is often lost in the talk of the embargo and travel bans and fines for traveling to Cuba are the dedicated people who have much in common with many around the world, those bound together by a love of nature and wild areas that transcends boundaries of capitalism and socialism, rich and poor, Spanish and English.

What is also lost in all the political talk is unspoiled Cuba itself, an island that the Caribbean's first tourist, Christopher Columbus, called "the most beautiful land eyes have ever seen." I would not disagree. Heavily forested mountains plunge down to the crashing waves of the coast, with only the footpaths of the gujiros and their animals crisscrossing the mountains. The land is one of swaying Royal palms, limpid water, languid sunsets, mists, rain, swift rivers and broad fields of sugar cane.

"Eastern Cuba is some of the last great Caribbean wilderness," Martin Davies, head of the Royal Society for the Protection of Birds, told me. "It is absolutely wonderful."

The wonders include 350 species of birds, 24 of them endemic to Cuba, 1,468 species of snails, including the rare, colorful polymita, the endangered Cuban crocodile, tens of thousands of pink flamingos, and the Cuban solenodon, or almiqui, a strange, snout-nosed 19-inch nocturnal mammal recently rediscovered after having been thought extinct. And perhaps, just perhaps, there is somewhere in these pristine mountains that holy grail of birdwatching, the ivory-billed woodpecker.

"Our goal is to bring in sustainable tours based on protecting the environment," said Flora and Fauna's Garcia Sardina. She explained that Flora and Fauna ministry has a budget in the millions of pesos (26 pesos to the dollar) and is proactively protecting areas they find valuable for ecology. Some are national heritage sites, others national parks, and still more "resource centers."

And protecting the environment is what Cuba is doing. While Havana harbor is heavily polluted and cars and trucks on the island belch unappealing black diesel exhaust, fly from the capital to the Sierra Maestra mountains and you will see miles of untouched land, including coastal mangrove swamps so vital to birdlife. At the southwest end of the island is the huge Disembarkation National Park. The day after my waterfall episode, we went hiking in the Sierra Maestra, near the base of Pico Turquino, Cuba's highest mountain.

Scattered throughout the area are many pre-Colombian caves and archeological sites yet to be excavated; in one was found a mysterious artifact called "Idol of the Aqua." Following the limestone path from one of the caves, our guide suddenly raises his hand. Somehow hearing a sound that no one else does, he peers through the trees and points. Using binoculars, I see my first Cuban pygmy owl. What a thrill to watch this beautiful bird up close, its head turning nearly all the way around as it scans the surrounding jungle. Farther down the path, he points out the Cuban trogon, and I think; this guide is an apt symbol of the Cubans I met during my week at TurNat; committed, dedicated, with an almost preternatural sensitivity to protecting the environment.

At the conference, I asked a question: "Are you ready for the more than a million Americans who would come to Cuba the first year the embargo is lifted?"

"Tell them to come," the speaker replies. "We want everyone to come, to see what we are striving for and how we are protecting our natural environment. If Americans come, they will find us awaiting them with open arms."