As you cruise along the Orinoco, South America's second-longest river, you will pass an imposing 17th-century fort. Just up the river is Ciudad Guayana, your gateway to Angel Falls. The falls, discovered 60 years ago by American bush pilot Jimmy Angel, are the hightest in the world. More than a half-mile hight and 15 times taller than Niagara Falls, they are undoubtedly one of the world's most breathtaking natural wonders.