It's easy to see why the isolated Galapagos Islands, made famous by Charles Darwin, were the first place on the planet to be named a United Nations Educational Scientific and Cultural Organization World Heritage Site.
The Galapagos, located 600 miles off the coast of Ecuador, are comprised of 13 major islands.
Since Darwin's arrival in 1835, the Galapagos have been called a "living laboratory of evolution" because of the extraordinary creatures found only on these islands.
Long before Darwin, the islands were home to the Galapagos giant tortoise, which can weigh up to 500 pounds and live for 150 years. There were about 300,000 tortoises on the islands when Darwin arrived in 1835; now the number has dwindled to 3,000. The reason: man.
In the 19th century, sailors harvested the tortoises for food.
Today, the Galapagos face a different kind of threat: tourism.
While the Galapagos hosted 10,000 visitors 30 years ago, last year there were 161,000 visitors. They brought in approximately $350 million, a vast sum for this struggling country.
To support tourism, the local population has grown from a modest 5,000 to 30,000.
Unbeknownst to many tourists, the island does not have a sewage system. Sewage is left to seep into the ground and the sea. With the spike in tourism, the Galapagos' pristine landscape is in danger of being transformed.
Which is why last year, UNESCO put the Galapagos on its list of Heritage Sites in Danger. The move was intended to raise awareness about the need for conservation and protection of its rare ecology.
Eliecer Cruz, governor of the Galapagos and former director of the Galapagos office of the World Wildlife Fund, has made conservation and protection of the islands' unique wildlife a priority. He told ABC News that, far from being offended by UNESCO's warning, he is pleased.
"It has been positive because it has strengthened the government's case to limit population growth and control tourism," Cruz said.
To regulate tourism, the government now allows just 84 licensed boats to take tourists around the islands. In addition, every visitor must be escorted by a trained guide.
Susan Roux, a tourist visiting the islands from Monterey, Calif., knows the rules: stay on the trails, don't use flash cameras, don't touch or feed the animals.
"I try really hard to do everything they tell us to do -- not get too close," Roux said. "But in the back of my mind, I still worry about it,"
Eco-tourists, like Roux, are clamoring to see a place where the animals are unafraid. Here, sea lions waddle right to the feet of humans, beg for scraps from local fishermen, and even sleep on park benches.
In so many ways, these islands are just as magical today as they were when Darwin set foot on them almost two centuries ago. But increasingly, the challenge is to keep them just as they are.