Don't ask mountaineers why they climb mountains. Chances are, you won't get an answer any more definitive than Everest explorer George Mallory's: "Because it's there." Scrambling to a summit isn't meant to be explained. It's meant to be experienced.

"Sometimes a climber sees a peak and just somehow feels inspired to climb it," says world-class mountaineer Greg Slayden. His web site Peakbagger.com contains a database of more than 18,000 mountain peaks as well as a personal log of hundreds of climbs, including Mt McKinley and 70 other summits over 12,000 feet. Slayden says his climbs are inspired by his love of nature, scenery, friendship, exercise, challenges and, perhaps most important, the wonderful feeling of accomplishing something big, of getting something done, of looking back up from the valley and thinking, "I did that."

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You can do it, too. Mountain climbing isn't all ropes, harnesses and ice picks. Some of the world's highest and most spectacular summits are just a long and strenuous walk away. Every corner of the world offers opportunities, and in the US, where both the Rockies and the Sierra Nevada await trekkers, there are literally hundreds of places to make it to the top. Colorado alone has 53 'fourteeners,' peaks over 14,000 feet high. Many are accessible with no technical skills, including the 15th highest, Longs Peak, which Slayden heartily recommends.

Getting Permission

Many popular mountain treks, especially those that go through protected areas or parks, require advance reservations and/or permits. At Mount St Helens, for example, you need a reservation to go higher than 4,800 feet. In Asia and Africa, you may need to navigate paperwork and collect a host of permits, since governments regard them as a revenue stream.

Where to Go

In researching possible treks, especially in the US and Canada [Images], look for the Yosemite Decimal System, which rates the difficulty of a climb from 1, an easy hike, to 5, an expert technical free climb with ropes and other gear. The hikes we've selected include trips rating from 1 to 3, with 3 signifying a 'scramble,' where at times you'll need to use your hands to pull yourself up and along. But no mountaineering skills are required.

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What to Bring

When researching what you'll need, study the weather -- not just for the region, but also at every level of altitude you'll reach. On Borneo's 13,698-foot Kinabalu, for example, you start in a tropical cloud forest and end up on a windswept granite ridge that may have snow on it. Be ready.

Keeping Safe

It's vital to consider worst-case scenarios. What if you break your ankle at 19,000 feet on Argentina's Aconcagua? How fast could you get off Kilimanjaro, if you had to? On guided journeys, require contingency plans from the tour company in writing. Double-check your health insurance, especially as it relates to emergency evacuations from remote areas or foreign countries. American climbers can also join the American Alpine Club and buy rescue insurance, a concept that first took hold with European climbers adventuring in the Alps.

Greg Slayden points out that on the most popular peaks anywhere in the world, help usually isn't very far away. In the US, if local rangers can't get you out, they'll typically call in the military, which will use the opportunity as a training exercise for its soldiers (at no cost to you). In remote areas of Africa or Asia, your options may be limited.

But above all else, prepare to be dazzled. Our picks of the most memorable mountain treks cover a variety of experiences on five continents: accessible day trips that can be part of a longer vacation, unique journeys into remote jungles, even an epic three-week adventure to the highest spot in the Americas. From the summits, you'll view smoking calderas, vast expanses of ocean and other peaks reserved for the most daring mountaineers. Let the view put everything into perspective. Get inspired. Take a few deep breaths. As TS Eliot put it, "In the mountains, there you feel free."

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