Some of the world's most treasured, remote landscapes can't be seen by helicopters, cars or even mountain bikes. These sacred places, like Ciudad Perdida, Everest's Base Camp and the top of Huayna Picchu, can only be reached on two feet. Although these climbs are open to the public, they're definitely not a walk in a park. Described as gut-wrenching, adrenaline-pumping and severely-challenging even for the fittest, most experienced hikers, every winded breath makes the view from the top and every near-teary eyed step fighting the incline worth it.

"Ciudad Perdida Hike" by William Neuheisel via Flickr Creative Commons

Ciudad Perdida, Colombia

One of the world’s most challenging hikes, the trek up to Colombia’s Lost City (Ciudad Perdida) is not for the faint of heart. The hike, which can take anywhere from five to seven days, takes hikers up a staggering 3,937 feet in sticky, humid and often unpredictable South American weather. The trail weaves through narrow forest passageways, up steep and uneven paths and will even have you traversing rivers. In the dry season, the river crosses are just knee-deep, however, if you’re visiting during wet season (October/November), you may be wading through rushing rapids up to your chest. Try to spend as much time as possible at the top of the ruins, known as Teyuna, to absorb the panoramic views of the lush mountain countryside.

Go with: G Adventures. This small-group, adventure-based company takes you deep into the jungle and up to Ciudad Perdida with a local Colombian guide. You'll enjoy tales of the lost city and all meals, accommodations and snacks are included in the price.

Everest Views

Everest's Base Camp, Nepal

A bucket-list item for the most intrepid travelers, Everest’s daunting 17,590-foot summit is one of the most challenging, and rewarding, hikes on the planet. Depending on the tour you choose, the hike can take anywhere from 13 – 16 days – starting in Lukla, Nepal and ending at base camp. The trek winds through challenging terrain that includes icy trails, snow-packed mountains, rushing river rapids, avalanches, and up steep and uneven climbs. Luckily, there’s ample downtime and overnight stays in quaint Nepalese villages, like Kathmandu, where you can gaze up at the stars above the stunning Himalayan peaks to take in the unique Sherpa culture. The view of Mount Everest from the top is astounding, and leaves even the most seasoned travelers at a loss for words.

Go with: Intrepid Travel. The 15-day tour fully immerses you in the culture of the people and the sherpas. You'll stay in local villages, take guided walks to other landmarks (like Gokyo lake) and have the unique opportunity to talk with people who live near the base year-round.

Paine Circuit Trek, Torres del Paine, Chile

Spanning over 75-miles through some of the world’s most beautiful scenery, the Paine Circuit Trek (also known as "the loop") winds you through the most iconic mountains, valleys and peaks of Torres del Paine National Park in Chilean Patagonia. The hike takes about seven days to complete, with rest days in between, and includes some of the park’s biggest highlights – John Gardner Pass, the Grey and Dickson Glaciers and the famous Torres del Paine “horns” or towers. Although beautiful, the hike is extreme – with steep, almost 90-degree uphill climbs on rocky footpaths. For many, the icy river crossings, slippery snow cover, and unpredictable weather (it’s said you can feel all four seasons during this trek) is too much to handle.

Go with: Friends. Although tricky, the Paine Circuit Trek is well marked, and there are ample sites set up throughout to camp.

Huayna Picchu, Peru

When it comes to epic hikes, the Incan trail undoubtably always makes the list and is a favorite among young adventurers and backpackers. Lesser known but immensely more challenging is the hike up Huayna Picchu, the green sloping mountain that flanks the back of the famous ruins. Dubbed “the hike of death,” the trek takes you up over 1,000 feet on an old Incan staircase carved from granite and slippery stones. The trek up is difficult on it's own, but the hardest part comes if you continue all the way down into the caves below, which welcome another set of challenges – mist, cloud cover, tropical showers, and exposed corners. It’s worth it when you have the ruins all to yourself, though.

Go with: Intrepid Travel. Their group size is small (just five to eight people), so the experience will feel far more personalized. Led by a local guide, he'll be able to offer personal intel into the iconic world wonder.

"Bhutan - DochuLa Pass" by Göran Höglund (Kartläsarn) via Flickr Creative Commons

Snowman Trek, Bhutan

Encompassing almost 200 miles, the Snowman Trek is known throughout the adventure community as one of the most challenging hikes in the world. Even for the fittest travelers, the trek takes almost a month to complete (19 – 24 days) and you remain at an altitude of over 13,000 feet the whole time. For hikers though, it's a pilgrimage every April to October for the views, which highlight the temples of Bhutan, the snow-capped Himalayas, lush forest, and rushing streams. Not for those scared of heights, the highest points of the trail are Tsochena and Jicchu Dramo camps, which are both over 16,000 feet.

Go with: World Expeditions. These outdoor experts lead you through the tricky and challenging terrain with ease. You'll be immersed in the ambiance with homestays and local meals.

"Grand Canyon National Park: S. Kaibab Trail 0090" by Grand Canyon National Park via Flickr Creative Commons

Bright Angel Trail, Arizona

For some, a 9.5-mile hike may seem like a breeze, especially compared to the others on this list. But the Bright Angel Trail in the Grand Canyon can be just as challenging given the conditions and terrifying drops. Temperatures can soar well over 110 degrees F, and due to the influx of visitors, many don’t come prepared – resulting in hundreds of heat related injuries and fatalities a year. For those that know what they're getting themselves into, the two to three hour hike reaches an altitude of 4,500 feet and takes you past the gushing Colorado River until you reach the view point at the top – where you’re met with 360-degree views of the multi-hued canyon.

Go with: A park ranger! Due to the climate, the Grand Canyon offers guide-led walks on many of the trailheads. Learn more here.

Laugavegurinn/Fimmvorduhals Pass, Iceland

Once relatively unchartered territory, Iceland is now one of the hottest tourist destinations for outdoor lovers and adventure seekers. For unparalleled views of the sporadic snow-capped gorges, cloud-covered mountain tops, volcanic valleys, gradient hillsides, waterfalls, and verdant green countryside, tackle the 34-mile hike through the Laugavegurinn/Fimmvorduhals Pass. The hike takes about four days to complete, but the landscape is as varying as the climate, with slippery hillsides, bubbling sulfur pots, deep river bends and more.

Go with: A friend! This trail is easy to navigate without a guide and going on your own gives you more time for epic selfies.

"Mount Ossa" by J Brew via Flickr Creative Commons

Overland Track, Australia

One of the most famed bush hikes in Australia, the Overland Track has earned a rightful place on the world's radar. Totaling 40 miles, this rocky and rugged climb takes you through Tasmania’s varying landscape, from Cradle Valley to Lake St. Claire. The four to six day hike takes you past some of the most beautiful scenery in the country where you'll see gushing waterfalls, deep valleys (either green and lush or cold and snow-packed) and jaw-dropping summits. The main peak is Mt. Ossa, which reaches an astonishing height of over 5,300 feet (and is the highest point in Tasmania). The best time to go is November – April, where the weather is milder and longer days provide more daylight.

Go with: Wilderness Expeditions, whose will accompany you with a local Tasmanian expert.