On August 16, 2008, a flash flood ripped down Havasu Canyon, a popular destination along the Grand Canyon's South Rim. Water levels swelled. A small earthen dam burst. And within hours a few dozen hikers were forced to evacuate in a Blackhawk helicopter. Though a very rare occurrence, the flood is a telling one: The Grand Canyon is a lot more than calendar-worthy viewpoints. It is one of the nation's most rugged wildernesses, vast and unpredictable. To see it in all its glory, you have to leave the comfort (and crowds) of the rim behind. The essence of the Grand lies in its depths.

GAME PLAN: Few wilderness trails anywhere elicit as much praise as the Nankoweap Trail. Those who have hiked the North Rim–to–river route speak of crowd-free camping in the heart of Marble Canyon. Then in the same breath, they recall the grueling elevation loss and gain, harrowing traverses, and challenging route-finding. Conclusion: This is an experts-only trail but an absolute must-do. From the West Nankoweap trailhead, the path drops 14 miles and 6,000 feet. Most hikers take two days for the descent, two for the climb back out, and one as a layover. As you dip below the North Rim, you'll first pass through aspen and ponderosa pine, then start switchbacking and corkscrewing down slopes of Supai sandstone and steeper faces of Redwall limestone. The going is tricky—look for cairns when the trail is less than obvious—but the views of buttes and red-rock temples are superb. Your camp is on a sandy beach near Nankoweap Rapids, overlooked by a set of 900-year-old ancestral Puebloan granaries. On the return trip, overnight at Nankoweap Creek, and be sure to top up your water bottles for the last 10.6 dry miles back to the rim.

Vitals: Seven-day visitors pass, $25. Backcountry permits are necessary for overnight trips into the canyon ($10, plus $5 per person per night; nps.gov/grca). Note that the North Rim is closed from mid-October to mid-May.

The Must-Do: With a park permit visitors can camp right on Ruby Point, 30 miles from the crowds of the South Rim developed area. The sweeping overlook is stunning, especially at dawn when the morning sun first hits Sagittarius Ridge and Point Sublime.

Base Camp: Built by the Santa Fe Railway to lure travelers west, the El Tovar Hotel has been wowing visitors since 1905. Its Oregon pine facade, broad terraces, and swarthy hunting lodge decor are proof that some things never go out of style (doubles from $174; grandcanyonlodges.com).

BONUS QUIZ: Think you know Grand Canyon National Park? Test yourself with this quiz.