Just outside swanky Aspen, Colorado, you'll find one of the nation's most indulgent, secluded – and totally natural – spa treatments. Conundrum Hot Springs is a series of clear, tepid pools surrounded by stunning mountain peaks nestled deep in the Maroon Bells-Snowmass Wilderness Area. But you have to sweat to get there – the 8.5-mile trek to the springs gives you a killer workout while keeping out the crowds, and the prize at the top is well worth the exertion.

The hike is best – and many years only doable – July through October, when the trail is driest and there's little lingering snow. Midweek promises the fewest hikers. Load up the backpacks for an overnight or two, but pack smart and sparingly – tent, grub, and a pouch of cheap wine are necessities – because you'll be lugging your gear from the trailhead at 9,000 feet to about 11,200 feet where the hot springs await. Start your trek in the early a.m. to beat the lightning and hail storms that often swoop in at midday. The first five or six miles are a slow, steady incline through thick woods, and then the final stretch kicks your ass with steeper rises and rockier terrain. Hang tough, though – you're close, and you're in total awe of the parabola of 13,000- and 14,000-foot peaks now splayed out before you.

Finally, you'll reach a Jacuzzi-sized lower pool and then a much larger, warmer upper pool with 16 campsites smattered around but spaced far enough apart to provide ample privacy. Claim a spot, set up camp, and then get thee to the upper spa to be engulfed by 102-degree mountain spring water. Just lie back, look up and the rest is history. Most days you'll be joined by a few fellow soakers, which means it can quickly turn into a rollicking happy hour. Just don't be shocked by topless gals or free-floating dudes: Clothes are definitely optional in this hippie dip. But after a few hours of spirited conversation and eased inhibitions (here's where the wine comes in), unbridled body parts will seem normal and you may just find yourself ditching the trunks. Once the sun sets, you'll see more stars than you ever knew existed dancing around the jagged purple-gray mountaintops.

If you're up for more mountaineering the next morning – this time sans gear – you have your pick of peaks to summit. Conundrum and Castle are both gnarly but doable in a few hours' time. Or else, hey, there's zero shame in heading straight back to the pool.

Come time to reenter civilization, heading downhill may sound easier than climbing up, but with your pack's weight bearing down on you and no promise of spa time ahead, it too is a grind. But, of course, you wouldn't be here if you didn't relish in the burn. Once you're down mountain, roll back into Aspen, where a hard-earned Conundrum Red Ale from Aspen Brewing Company or a primo mojito on Sky Hotel's poolside deck will never have tasted so sweet.

More information: Visit selecthikes.com for directions and more information on Conundrum Hot Springs.