Closely interwoven bands of layered rock skirt a sea of gigantic ancient boulders, coming together to form a surreal panorama that melts into Arizona's vast landscape. From high above the topmost point of the canyon, the mighty Colorado River appears as a muddy sliver, belying the tumultuous nature of its waters that carved through ancient layers of rock and birthed the steep canyons surrounding it. Over several millennia, the river snaked its way through the rugged landscape, constantly deepening and pushing the edges of the canyon, oblivious that its aggressive course unraveled years of geological history. For years, the canyon was home to indigenous Native American tribes, before Spanish explorers and American trappers settled into the river basin. Today, the Grand Canyon continues to instill a deep sense of wonder and mystique in whoever visits it, an eternal ocean of auburn rock that spreads majestically under deep blue skies.

Sometimes called the necklace that adorns the northeastern Australian coast, the Great Barrier Reef is the largest in the world. It is a collection of more than 3,000 distinct reefs and island fleets, protected by the turquoise waters of the majestic Coral Sea. Together, the Great Barrier Reef was proclaimed a UNESCO World Heritage Site in 1981. Waters run shallow for a large portion of the reef, making the perfect environment for aquatic adventures before the reef dips to a depth of 2,000 meters (6,561 feet). Diving and snorkeling here are like being transported to a different world, where swirling, rainbow-colored corals create a colorful backdrop for so many fish species. The experience is bound to stay for a lifetime.

Rising 390 feet (120 meters) above the blue waters of the Atlantic, the Cliffs of Moher (or Mohair) are truly majestic. Carved out of sandstone and suspended between the ocean and sky, the vertical cliffs capture nature's raw energy and untamed spirit. Named for the old Moher fort that once stood on the southern end of the cliffs, this ancient rock face overlooks the Twelve Pins and Maumturks mountain ranges, Galway Bay dotted with the Aran Islands, and Loop Head. Located along the Wild Atlantic Way with the ocean crashing beneath and birds calling above, it's easy to believe that the Cliffs of Moher are at world's end.

A magnificent silhouette against Africa's horizon, the colossal Mount Kilimanjaro lies at the heart of the eponymous national park. It is a sight to behold any time of the year, with its summit reaching a spectacular height of 19,341 feet (5,895 meters), making this Africa's highest peak. It is also the world's tallest freestanding mountain; a towering hulk of rock that rises from the otherwise flat terrain. Mount Kilimanjaro is actually a dormant volcano, with three volcanic cones - Mawenzi, Shira and Kibo - that descend into lush greenery and sprawling grasslands. The base of the mountain is sheathed in dense forests, the native habitat for a number of species including buffaloes, leopards, monkeys and elands. Each year, this towering beauty is known to attract more than 25,000 trekkers, of which only a few are able to scale the daunting slopes to the summit.

The ethereal beauty of the Yellowstone National Park unfolds one panorama at a time - sometimes in visions of raw, rugged alpine features, at other times, in softer landscapes clouded with billowing smoke that emanates from hot springs and geysers. Whatever the sight, there is little that will not mesmerize anyone who traverses the bounds of this park. Deemed to be the first national park in the world, the depths of Yellowstone were home to early Native Americans for a staggering 11,000 years, before mountain men and trappers ambled up its sheer cliffs and conducted organized explorations. It stretches from the state of Wyoming and spills over the boundaries of both Montana and Idaho, a geographic testament to its profound sprawl. The Old Faithful, a cone geyser, is one of the park's main attractions, while the Yellowstone Lake stretches over a supervolcanic caldera. Speckled with gushing waterfalls, geothermal spots, majestically arched cliffs that cast arresting silhouettes, and an array of nature's vivid colors, the park is an unspoiled terrestrial spectacle.

The world's largest cave, Son Doong is vast enough to boast a micro-climate of its own that has spawned forests teeming with flying foxes and monkeys. This impressive cave is 5.5 miles (8.9 kilometers) long and can fit an entire city block within its cavernous embrace. The rays of light that filter through have spurred the growth of trees, while dried pools once fed by the subterranean river boast massive cave pearls. The stalagmites too are of grand proportions, measuring up to 80 meters (262.4 feet) in height. With its own jungles and rivers enclosed beneath a sky of rock, the Son Doong Cave is truly a mesmerizing destination for the adventurous at heart. The cave is notoriously difficult to reach, however, and expeditions are led by Oxalis, a local travel company that has exclusive access to the magical world of the Son Doong Cave.

The thundering waters of Niagara Falls tumble and plummet from heights of up to 51 meters (167 feet) and an average collective width of approximately 1204 meters (3950 feet) on the United States and Canada Border. One of the largest in the world, the falls are comprised of The Horseshoe Falls, the Bridal Veil Falls and the American Falls. Over 60,000 cubic meters (200,000 cubic feet) of water rush over the brink at an astonishing speed every minute. Each of the falls is unique and offer spectacular vistas of one of the world's most visited natural wonders. Come the winter holiday season, the falls are beguilingly decked out with a light show for the annual Winter Festival of Lights.

The world's largest waterfalls system, Iguazú Falls lie within sight of the point where the countries of Argentina, Brazil, and Paraguay meet. Legend has it, a long time ago a deity besotted with a beautiful woman was overcome with wrath when she fled with her lover in a canoe. The deity cut the river to stymie their escape, creating the falls and condemning the lovers to an eternal plunge. The Upper Iguazú River rushes down the steep face of the Devil's Throat, a narrow chasm of sheer rock, tumbling down in a series of cataracts and falls numbering in the hundreds. The tallest of these fall from a height of about 82 meters (269 feet) into the canyon below. A cacophony of rumbles and roars pervades the silence as the river comes crashing down, filling the air with a misty spray sliced by rainbows. A vision of immense beauty, the Iguazú Falls are a majestic display of nature's might; an awe-inspiring sight that attracts thousands to the midst of this monumental curtain of water.

Nestled in the Andes, Salar de Uyuni, also known as Salar de Tunupa, is the largest salt flat in the world, covering an area of 10 million square meters (107,639,104 square feet). This geological marvel dates back to approximately 25,000 years ago and was formed by evaporation of lakes that once covered the entire surface. Geometric formations of salt crystals stretch for miles and shimmer under the sun's glowing rays. The highly reflective surface is especially stunning in the rainy season, when the entire surface is covered by a film of water, turning the landscape into a giant mirror reflecting the clouds and blue sky. In dry months, the salt flats crack and create unique patterns that reflect the deep blue of the starry night. A natural landscape that evokes wonder, the Salar de Uyuni is the Altiplano region's crowning jewel.

Eisriesenwelt are the largest accessible ice caves in the world. The caves are buried in the depths of the Hochkogel mountain range and the labyrinthine tunnels extend for more than 40 kilometers (24 miles). Originally discovered by Anton von Posselt in 1879, the caves only gained prominence after they were 'rediscovered' by Alexander von Mörk in the early 20th Century. It's believed that the limestone cave system has been evolving for millions of years. As the temperature within the cave is always at sub-zero, when snow melts in the spring and drips into the cavern, it cools and freezes in a variety of fascinating sculptures. A stunning example of nature's grandeur, some caves are illuminated in an ethereal blue light that filters in; others are illuminated with lamps that cast strange shadows over the walls, as they bring into focus the weird and wonderful works of natural art .

An astonishing testament to the tempestuous side of nature, the Ngorongoro Crater is a colossal volcanic caldera that was born two to three million years ago. This gaping hole, resembling a giant eye socket, was the result of a seemingly self-destructive eruption that rendered the volcano to collapse, leaving behind a massive cavity in its wake. Straddling the natural wonders of the Ngorongoro Conservation Area and the expansive wilderness of the Serengeti, the crater finds itself in the midst of an incredibly rich geological landscape. The crater and its surrounds are home to a prolific mammal habitat endemic to the African continent, a remarkable flora, and a mineral-studded base that spawns vegetation fed on by wandering zebras and wildebeest. The collective beauty of the Serengeti and Ngorongoro invite hordes of visitors throughout the year who undertake the safari to view the conservation and its surrounds in its glorious raw beauty.

Hogar de un laberinto interminable de humedales subtropicales, el Parque Nacional Everglades cobija un enorme ecosistema bastante peculiar. En los inmensos pantanos del parque encontrarán manglares y un sólido sitio de reproducción y hábitat de diversas especies de aves y vida silvestre. Los ríos cubiertos de hierba alta y los pantanos densos esconden profundidades oscuras y tropicales, y son el hogar de cientos de especies de aves y de la elusiva pantera de Florida. Las hamacas de madera tropical forman el refugio perfecto para los reptiles, mientras que las praderas con sus aguas salobres fomentan el crecimiento de las suculentas, como la salicornia. Aunque las preocupaciones modernas como el calentamiento global y el aumento del nivel del mar ponen en riesgo su frágil ecosistema, el Parque Nacional Everglades es una fuente constante de belleza y maravilla para todos los que lo visitan.