There are 23 species of marine reptiles that inhabit the Great Barrier Reef including 6 species of sea turtles and 17 species of sea snakes. Occasionally, the saltwater crocodile also ventures out to forage on the reef, although such visits are quite rare.

The next day--July 24--after a tough climb to the mountain's ridge in cold and drizzly weather, Bingham met a small group of peasants who showed him the rest of the way. Led by an 11-year-old boy, Bingham got his first glimpse of the intricate network of stone terraces marking the entrance to Machu Picchu. The excited Bingham spread the word about his discovery in a best-selling book, sending hordes of eager tourists flocking to Peru to follow in his footsteps up the Inca trail. The site itself stretches an impressive five miles, with over 3,000 stone steps linking its many different levels. Today, more than 300,000 people tramp through Machu Picchu every year, braving crowds and landslides to see the sun set over the towering stone monuments of the "Sacred City" and marvel at the mysterious splendor of one of the world's most famous man-made wonders.

Although the archaeological discovery of Machu Picchu came nearly a hundred years ago, historians are still unsure of the function of this ancient Inca citadel.The Inca had no system of writing and left no written records, and archaeologists have been left to piece together bits of evidence as to why Machu Picchu was built, what purpose it served, and why it was so quickly vacated.

It’s not actually the Lost City of the Inca.When the explorer Hiram Bingham III encountered Machu Picchu in 1911, he was looking for a different city, known as Vilcabamba. This was a hidden capital to which the Inca had escaped after the Spanish conquistadors arrived in 1532. Over time it became famous as the legendary Lost City of the Inca. Bingham spent most of his life arguing that Machu Picchu and Vilcabamba were one and the same, a theory that wasn’t proved wrong until after his death in 1956. (The real Vilcabamba is now believed to have been built in the jungle about 50 miles west of Machu Picchu.) Recent research has cast doubt on whether Machu Picchu had ever been forgotten at all. When Bingham arrived, three families of farmers were living at the site.