Great wildlife adventures to be had in the U.S. You need not venture to the peaks of Everest or roam the baking sands of the Sahara in search of adventure. Within its 3.79 million square miles, the United States of America contains an abundance of vast, wild and untamed landscapes waiting to be discovered. The list of possibilities for adventure is virtually endless, but here are four of the best. Rafting the Grand Canyon Navigating the rushing waves of the Colorado River as it passes through America's most famous natural wonder is truly a once-in-a-lifetime experience. Nowhere is the majestic beauty of nature more evident than from the foot of this gargantuan canyon, with the waters of the river underneath propelling you on a route carved out over two billion years. The journey offers both tranquility and chaos, as violent rapids give way to peaceful stretches of gentle water. Most trips last between 3 and 18 days and cover different sections of the river, depending on ability and experience. Check out Action Whitewater Adventures for more. Hiking Yosemite's Half Dome The rocky peak of Yosemite's Half Dome offers adventure seekers one of nature's great challenges. In fact, in an 1865 report the treacherous summit was deemed "perfectly inaccessible," according to the National Park Service. A century-and-a-half later, thousands of adventure-seeking climbers prove this assessment wrong every year by scaling the 4,700 foot peak. The 17-mile round trip is no easy task and should not be attempted by the inexperienced hiker. However, the rewards are worth the strain, with breathtaking views of Vernal and Nevada Falls, as well at the magnificent rock formations of the Half Dome itself. Along the way, climbers can discover the varied nightlife of America's most celebrated national park, while climbers can enjoy spectacular views of the Yosemite Valley and the High Sierra for the Half Dome's peak. Exploring the Alaskan Wilderness At the gate of the Arctic, wolves, caribou, bears and foxes all inhabit the sweeping open plains and desolate mountains of the Alaskan wilderness. The Arctic National Wildlife Reserve was created to preserve some of the United States most diverse and beautiful wildlife and wilderness. The park offers adventurers a rare opportunity to enjoy complete seclusion, days away from hustle and bustle of human civilization, to gain an unadulterated glimpse at one of the country's most breathtaking natural wonderlands. Climbing Denali North America's highest peak is no easy climb. Base cap sits at an elevation of roughly 7,000 feet on the periphery of a glacier, where climbers begin the long and arduous ascent up the West Buttress to the summit at 20,300 feet. There journey is long, usually taking days to complete. Meanwhile climbers must set up camp on the mountainside and brave harsh winds and icy snows while en route to the summit. Needless to say, the views are spectacular, particularly on clear day, where the lush surrounding parkland can be surveyed for miles.